Copy exportable artifacts to module sdk snapshot

This change modifies the copy rules of the sdk_library when generating
the module sdk snapshots so that the exportable artifacts (annotations
zip, api file, removed api file, srcjar file) are copied instead of the
everything artifacts.

In order to satisfy the prebuilts compatibility, this feature is flag
guarded by the build flag "RELEASE_HIDDEN_API_EXPORTABLE_STUBS"

Test: m --no-skip-soong-tests
Bug: 315027929
Change-Id: I8bf5bb1f196aa9b5db78ba4677caa5f4337e3021