Auto-conform @ExpoModule classes to AnyModule

[tsapeta]

Summary

Stacked on top of #4. Two commits:

1. Auto-conform @ExpoModule classes to AnyModule — emits extension MyModule: AnyModule {} when the class doesn't already inherit from Module, BaseModule, or AnyModule. Replaces the inheritance-required diagnostic from Diagnose missing Module inheritance on @ExpoModule classes #4 with permissive expansion.

2. Synthesize appContext, init(appContext:), and @ModuleDefinitionBuilder — the macro now fills in everything BaseModule used to provide, so a @ExpoModule class can stand on its own without inheriting from BaseModule. Skips emission when the user provided any of these themselves.

Together these two steps unblock @ExpoModule for classes that need to author the module surface without committing to a specific superclass.

// Minimum: works without any inheritance line
@ExpoModule
final class MyModule {
  func definition() -> ModuleDefinition {
    Name("MyModule")
  }
}

// Expands to:
final class MyModule {
  public weak var appContext: AppContext?

  public required init(appContext: AppContext) {
    self.appContext = appContext
  }

  @ModuleDefinitionBuilder
  func definition() -> ModuleDefinition {
    Name("MyModule")
  }

  public func _exposedDefinition() -> [AnyDefinition] {
    return [
      Name("MyModule")
    ]
  }
}

extension MyModule: AnyModule {}

What gets skipped, and when

User wrote	extension: AnyModule	appContext	init(appContext:)	@ModuleDefinitionBuilder
: Module	skip (already conforms)	skip (BaseModule provides)	skip (BaseModule provides)	stamp
: BaseModule	skip (provides via BaseModule)	skip	skip	stamp
: AnyModule	skip (already conforms)	emit	emit	stamp
: SomeOtherBase	emit	emit	emit	stamp
no inheritance	emit	emit	emit	stamp
user wrote own appContext	(orthogonal)	skip	(orthogonal)	(orthogonal)
user wrote own init(appContext:)	(orthogonal)	(orthogonal)	skip	(orthogonal)
user already stamped @ModuleDefinitionBuilder	(orthogonal)	(orthogonal)	(orthogonal)	skip

Test plan

• swift test passes — 27 cases total (8 new across the two commits).
• In a consumer module that uses @ExpoModule without : Module, the iOS build succeeds and JS calls round-trip.
• In a consumer that writes : Module explicitly, no "redundant conformance" or duplicate-member errors appear.
• A consumer that hand-rolls one of appContext / init(appContext:) / @ModuleDefinitionBuilder doesn't get a duplicate from the macro.