Marks recursive error causes in stringified errors, as requested in #13413, eg.

error: Uncaught Error: baz
const baz = new Error("baz", { cause: bar });
            ^
    at file:///error_cause_recursive_tail.ts:3:13
Caused by: Error: bar <ref *1>
    at file:///error_cause_recursive_tail.ts:2:13
Caused by: Error: foo
    at file:///error_cause_recursive_tail.ts:1:13
Caused by: [Circular *1]

We have to compare 2 JsError objects for equality (But not their cause) in order to find a recursive error.
That's what I added JsErrorIdentity for. I personally dislike this struct, but couldn't find a better solution. Perhaps someone familiar with deno's codebase and Rust has a better idea.

Additional changes

• Renamed parameter of format_js_error_inner(), because it confused me more than once