…etry#35544)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->

As described at
open-telemetry#35491,
it is useful to provide the option to the users for defining
`receiver_creator`'s templates per container.

In this regard, the current PR introduces a new type of Endpoint called
`PodContainer` that matches the rule type `pod.container`. This Endpoint
is emitted for each container of the Pod similarly to how the `Port`
Endpoints are emitted per container that defines a port.

A complete example on how to use this feature to apply different parsing
on each of the Pod's container is provided in the `How to test this
manually` section.

**Link to tracking Issue:** <Issue number if applicable> Fixes
open-telemetry#35491

**Testing:** <Describe what testing was performed and which tests were
added.> TBA

**Documentation:** <Describe the documentation added.> TBA


### How to test this manually

1. Use the following values file to deploy the Collector's Helm chart
```yaml
mode: daemonset

image:
  repository: otelcontribcol-dev
  tag: "latest"
  pullPolicy: IfNotPresent

command:
  name: otelcontribcol

clusterRole:
  create: true
  rules:
   - apiGroups:
     - ''
     resources:
     - 'pods'
     - 'nodes'
     verbs:
     - 'get'
     - 'list'
     - 'watch'
   - apiGroups: [ "" ]
     resources: [ "nodes/proxy"]
     verbs: [ "get" ]
   - apiGroups:
       - ""
     resources:
       - nodes/stats
     verbs:
       - get
   - nonResourceURLs:
       - "/metrics"
     verbs:
       - get

extraVolumeMounts:
 - name: varlogpods
   mountPath: /var/log/pods
   readOnly: true

extraVolumes:
  - name: varlogpods
    hostPath:
      path: /var/log/pods

config:
  extensions:
    k8s_observer:
      auth_type: serviceAccount
      node: ${env:K8S_NODE_NAME}
      observe_nodes: true
  exporters:
    debug:
      verbosity: basic
  receivers:
    receiver_creator/logs:
      watch_observers: [ k8s_observer ]
      receivers:
        filelog/busybox:
          rule: type == "pod.container" && pod.labels["otel.logs"] == "true" && container_name == "busybox"
          config:
            include:
              - /var/log/pods/`pod.namespace`_`pod.name`_`pod.uid`/`container_name`/*.log
            include_file_name: false
            include_file_path: true
            operators:
              - id: container-parser
                type: container
              - type: add
                field: attributes.log.template
                value: busybox
        filelog/lazybox:
          rule: type == "pod.container" && pod.labels["otel.logs"] == "true" && container_name == "lazybox"
          config:
            include:
              - /var/log/pods/`pod.namespace`_`pod.name`_`pod.uid`/`container_name`/*.log
            include_file_name: false
            include_file_path: true
            operators:
              - id: container-parser
                type: container
              - type: add
                field: attributes.log.template
                value: lazybox
  service:
    extensions: [health_check, k8s_observer]
    pipelines:
      logs:
        receivers: [receiver_creator/logs]
        processors: [batch]
        exporters: [debug]
```
2. Follow the logs of the Collector's Pod i.e: `k logs -f
daemonset-opentelemetry-collector-agent-2hrg5`
3. Deploy a sample Pod which consists of 2 different containers:

```yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: daemonset-logs
  labels:
    app: daemonset-logs
spec:
  selector:
    matchLabels:
      app.kubernetes.io/component: migration-logger
      otel.logs: "true"
  template:
    metadata:
      labels:
        app.kubernetes.io/component: migration-logger
        otel.logs: "true"
    spec:
      tolerations:
        - key: node-role.kubernetes.io/master
          effect: NoSchedule
      containers:
        - name: lazybox
          image: busybox
          args:
            - /bin/sh
            - -c
            - while true; do echo "otel logs at $(date +%H:%M:%S)" && sleep 0.1s; done
        - name: busybox
          image: busybox
          args:
            - /bin/sh
            - -c
            - while true; do echo "otel logs at $(date +%H:%M:%S)" && sleep 0.1s; done
```

Verify in the logs that only 2 filelog receivers are started, one per
container:

```console
2024-10-02T12:05:17.506Z	info	[email protected]/observerhandler.go:96	starting receiver	{"kind": "receiver", "name": "receiver_creator/logs", "data_type": "logs", "name": "filelog/lazybox", "endpoint": "10.244.0.13", "endpoint_id": "k8s_observer/01543800-cfea-4c10-8220-387e60f65151/lazybox"}
2024-10-02T12:05:17.508Z	info	adapter/receiver.go:47	Starting stanza receiver	{"kind": "receiver", "name": "receiver_creator/logs", "data_type": "logs", "name": "filelog/lazybox/receiver_creator/logs{endpoint=\"10.244.0.13\"}/k8s_observer/01543800-cfea-4c10-8220-387e60f65151/lazybox"}
2024-10-02T12:05:17.508Z	info	[email protected]/observerhandler.go:96	starting receiver	{"kind": "receiver", "name": "receiver_creator/logs", "data_type": "logs", "name": "filelog/busybox", "endpoint": "10.244.0.13", "endpoint_id": "k8s_observer/01543800-cfea-4c10-8220-387e60f65151/busybox"}
2024-10-02T12:05:17.510Z	info	adapter/receiver.go:47	Starting stanza receiver	{"kind": "receiver", "name": "receiver_creator/logs", "data_type": "logs", "name": "filelog/busybox/receiver_creator/logs{endpoint=\"10.244.0.13\"}/k8s_observer/01543800-cfea-4c10-8220-387e60f65151/busybox"}
2024-10-02T12:05:17.709Z	info	fileconsumer/file.go:256	Started watching file	{"kind": "receiver", "name": "receiver_creator/logs", "data_type": "logs", "name": "filelog/lazybox/receiver_creator/logs{endpoint=\"10.244.0.13\"}/k8s_observer/01543800-cfea-4c10-8220-387e60f65151/lazybox", "component": "fileconsumer", "path": "/var/log/pods/default_daemonset-logs-sz4zk_01543800-cfea-4c10-8220-387e60f65151/lazybox/0.log"}
2024-10-02T12:05:17.712Z	info	fileconsumer/file.go:256	Started watching file	{"kind": "receiver", "name": "receiver_creator/logs", "data_type": "logs", "name": "filelog/busybox/receiver_creator/logs{endpoint=\"10.244.0.13\"}/k8s_observer/01543800-cfea-4c10-8220-387e60f65151/busybox", "component": "fileconsumer", "path": "/var/log/pods/default_daemonset-logs-sz4zk_01543800-cfea-4c10-8220-387e60f65151/busybox/0.log"}
```

In addition verify that the proper attributes are added per container
according to the 2 different filelog receiver definitions:


```console
2024-10-02T12:23:55.117Z	info	ResourceLog #0
Resource SchemaURL: 
Resource attributes:
     -> k8s.pod.name: Str(daemonset-logs-sz4zk)
     -> k8s.container.restart_count: Str(0)
     -> k8s.pod.uid: Str(01543800-cfea-4c10-8220-387e60f65151)
     -> k8s.container.name: Str(lazybox)
     -> k8s.namespace.name: Str(default)
     -> container.id: Str(63a8e69bdc6ee95ee7918baf913a548190f32838adeb0e6189a8210e05157b40)
     -> container.image.name: Str(busybox)
ScopeLogs #0
ScopeLogs SchemaURL: 
InstrumentationScope  
LogRecord #0
ObservedTimestamp: 2024-10-02 12:23:54.896772888 +0000 UTC
Timestamp: 2024-10-02 12:23:54.750904381 +0000 UTC
SeverityText: 
SeverityNumber: Unspecified(0)
Body: Str(otel logs at 12:23:54)
Attributes:
     -> log.iostream: Str(stdout)
     -> logtag: Str(F)
     -> log: Map({"template":"lazybox"})
     -> log.file.path: Str(/var/log/pods/default_daemonset-logs-sz4zk_01543800-cfea-4c10-8220-387e60f65151/lazybox/0.log)
Trace ID: 
Span ID: 
Flags: 0
ResourceLog #1
Resource SchemaURL: 
Resource attributes:
     -> k8s.container.restart_count: Str(0)
     -> k8s.pod.uid: Str(01543800-cfea-4c10-8220-387e60f65151)
     -> k8s.container.name: Str(busybox)
     -> k8s.namespace.name: Str(default)
     -> k8s.pod.name: Str(daemonset-logs-sz4zk)
     -> container.id: Str(47163758424f2bc5382b1e9702301be23cab368b590b5fbf0b30affa09b4a199)
     -> container.image.name: Str(busybox)
ScopeLogs #0
ScopeLogs SchemaURL: 
InstrumentationScope  
LogRecord #0
ObservedTimestamp: 2024-10-02 12:23:54.897788935 +0000 UTC
Timestamp: 2024-10-02 12:23:54.749885634 +0000 UTC
SeverityText: 
SeverityNumber: Unspecified(0)
Body: Str(otel logs at 12:23:54)
Attributes:
     -> log.file.path: Str(/var/log/pods/default_daemonset-logs-sz4zk_01543800-cfea-4c10-8220-387e60f65151/busybox/0.log)
     -> logtag: Str(F)
     -> log.iostream: Str(stdout)
     -> log: Map({"template":"busybox"})
Trace ID: 
Span ID: 
Flags: 0
```

Signed-off-by: ChrsMark <[email protected]>