Refactor: Deduplicate gotask API definitions

[mpyw]

Problem

The gotask API list is defined in two separate locations with similar but slightly different metadata:

1. internal/apis.go - RegisterGotaskAPIs() (lines 71-89)

• Purpose: Used by spawnerlabel checker for spawner label validation
• Called from: analyzer.go:123
• Data structure: registry.Entry with AlwaysSpawns field
• APIs registered: DoAll, DoAllSettled, DoRace, DoAllFns, DoAllFnsSettled, DoRaceFns, Task.DoAsync, CancelableTask.DoAsync

2. internal/checkers/gotask.go - GotaskChecker.entries (lines 53-65)

• Purpose: Used by gotask checker for context propagation validation
• Called from: analyzer.go:196-200
• Data structure: gotaskEntry with Variadic and IsDoAsync fields
• APIs registered: Same list as above

Issues

1. DRY violation: The same API set is maintained in two places
2. Maintenance burden: Adding/removing gotask APIs requires changes in both locations
3. Inconsistency risk: The two lists could drift apart over time

Key Differences

While both define the same API set, they have different metadata requirements:

Aspect	RegisterGotaskAPIs	GotaskChecker.entries
DoAsync CallbackArgIdx	Not specified	0 (explicit)
Metadata fields	AlwaysSpawns	Variadic, IsDoAsync
Purpose	Spawner label detection	Context propagation checking

Proposed Solution

Create a unified gotask API registry that both checkers can consume:

1. Define a single source of truth for gotask APIs (e.g., internal/gotask/apis.go)
2. Provide adapter functions to convert to checker-specific formats:
   • ToRegistryEntries() → for spawnerlabel checker
   • ToGotaskEntries() → for gotask checker
3. Update both checkers to use the unified registry

This would maintain flexibility for checker-specific metadata while eliminating duplication.

Alternative

If the metadata requirements are too divergent, document why the duplication is necessary and add validation to ensure both lists stay in sync.