Restore __ANDROID_API__ guards for camera/media headers

Partial revert of "Add __INTRODUCED_IN to audio/camera/media headers.",
commit 85a41536.

Restore the API guards where they used to exist. I *could* add
__ANDROID_API__ around only the function declarations, which is what the
versioner would do, but the function declarations are mixed up with the
types and constants, so I'd need to add a bunch of __ANDROID_API__ checks
or reorganize the headers.

NdkMediaFormat.h and AAudio.h still have __INTRODUCED_IN symbols that
aren't guarded by __ANDROID_API__. Maybe those files should be reorganized
so they don't alternate between APIs so much.

Test: builds
Bug: http://b/111668906
Bug: http://b/113052379
Change-Id: I757a6097f7840ea50e2fc92db7defef493097672
Merged-In: I757a6097f7840ea50e2fc92db7defef493097672
(cherry picked from commit 0c9470ce)