[REQUIRED] Environment info

firebase-tools: 9.3.0

Platform: Docker container running on Windows 10

[REQUIRED] Test case

I launched a firebase emulator with docker.
I have specified a host to access from outside the container.

{
  "firestore": {
    "rules": "firestore.rules",
    "indexes": "firestore.indexes.json"
  },
  "hosting": {
    "public": "public",
    "ignore": ["firebase.json", "**/.*", "**/node_modules/**"]
  },
  "emulators": {
    "firestore": {
      "host": "0.0.0.0",
      "port": 8080
    },
    "hosting": {
      "host": "0.0.0.0",
      "port": 4200
    },
    "ui": {
      "enabled": true,
      "host": "0.0.0.0",
      "port": 3000
    }
  }
}

However, I cannot access the firestore emulator from the hosting emulator.

Emulator UI is accessing the firestore emulator at 127.0.0.1:8080.
However, hosting emulator is accessing the firestore emulator at 0.0.0.0:8080.

I think we need to make a similar fix here.
firebase/firebase-tools-ui#312

[REQUIRED] Steps to reproduce

1. Run firebase init
2. Select emulator, firestore, hosting
3. Add host config to firebase.json
4. Run firebase emulators:start

[REQUIRED] Expected behavior

I can access the firestore emulator from the hosting emulator.

[REQUIRED] Actual behavior

I cannot access the firestore emulator from the hosting emulator.