Allow framework-media to build the framework-media.impl

The framework-media java_sdk_library is currently api_only for legacy
reasons. This change allows it to also build the framework-media.impl
library by making the following changes:
* Adds impl_only_static_libs to allow the implementation to statically
  include other libraries, something no other java_sdk_library has
  needed to do.
* Passes the apex_availability property through to the impl library so
  it can be statically included in the updatable-media which is what is
  included in the apex, again for legacy reasons.

Bug: 190807367
Bug: 229932396
Test: m com.android.media media-module-sdk
      # Compare before and after this change (and corresponding change
      # to updatable-media/framework-media.
Change-Id: I9e1837edcca6f5fa84fc611274cf8fbba8a896b8