feat(functions): Implement TaskQueue Scopes

[inlined]

Description

This PR introduces Task Queue Scopes to the Firebase Admin SDK functions module. It decouples the legacy backward-compatible string-to-scope migration logic from the stateless client and isolates it inside the API wrapper layer (TaskQueue).

Key Changes

1. API Wrapper Retry & Upgrade (TaskQueue):
   • TaskQueue.enqueue() and delete() now capture 404 errors for legacy string parameters ('extensionOrKit' scope).
   • On a 404 error, they automatically retry using a temporary kit scope.
   • If the retry succeeds, the wrapper mutates the stateful scope to 'kit' and logs a legacy targeting warning.
2. Immediate Self-Targeting Warning:
   • Matches targeting parameters against process.env.EXT_INSTANCE_ID and process.env.KIT_INSTANCE_ID at construction time.
   • If self-targeting is detected, it logs an immediate deprecation/performance warning and mutates the scope immediately to 'extension' or 'kit', bypassing unnecessary 404 fallback call roundtrips.
3. Design style: chose to make the migration logic part of the API type and not the API internals type to more obviously collect what is transitionary/migration logic that can be removed later
4. Unit Tests:
   • Added unit tests verifying scope resolves to global if no environment variables are set.
   • Added unit tests verifying self-targeting warnings and direct namespaced resolution for both extensions and kits.

[gemini-code-assist]

Code Review

This pull request introduces a new FunctionScope type to represent the scope of a function in a task queue, deprecating the legacy extensionId string parameter. It updates FunctionsApiClient, Functions, and TaskQueue to support these scopes (including current, global, extension, and internal kit scopes) with fallback logic for migration, and adds comprehensive unit tests. The review feedback highlights a few issues and improvement opportunities: correcting a typo ('peformance') and an invalid scope value ({ scope: "self" } instead of { scope: "current" }) in warning messages (and their corresponding tests), removing a redundant type check in TaskQueue, and improving type safety in FunctionsApiClient by avoiding an as any cast through discriminated union narrowing.

[lahirumaramba]

Thank you for submitting this!
LGTM! Added a couple of comments.

[egilmorez]

Thanks, I do have some nits! :)