Report nested types in scan-exports

[tsapeta]

Fixes ENG-27128.

scan-exports only reported file-scope declarations. An Enumerable enum, @Record, @Union, or @SharedObject declared inside another type was missing, so every ref to it stayed unresolved (Encoding in expo-crypto's DigestOptions, NotificationType and ImpactStyle in expo-haptics' module).

• The surface visitor now walks type bodies (class, struct, enum, actor) and file-scope extensions. A nested type is reported under its qualified Swift name, for example Options.Encoding. A default jsName stays the declared name, as the macros spell it. Types local to a function body or a closure are still skipped.
• Only a file-scope @ExpoModule is reported, because autolinking registers no other.
• A ref resolves the way Swift looks a name up: from the type it is written in, outward to file scope (Self.X starts at the type itself). Encoding in Options finds Options.Encoding before a file-scope Encoding. A qualifier the scan does not declare is still dropped (Media.Status finds Status).
• A resolved ref's name is now the qualified name of its declaration, so a consumer finds the declaration by an exact match. A module's classes entry takes the qualified name of its shared object the same way. schemaVersion is now 7, and src/types.ts follows.

Test Plan

swift test in apple/ passes, with new tests for nested types, types in extensions, local types, scoped lookup and shadowing, and a module class nested in its module, and Self.-qualified refs. npm run typecheck passes.

[linear-code]

ENG-27128