Add prebuilt apk builtin hook

Checking in platform prebuilt APKs requires that the commit message
contains the APK's badging info, location of where it was built,
and whether or not it is suitable for public or preview release.

Bug: 111363405
Test: Unit tests pass
Test: Manual.  Enabled hook, tried to submit CLs with different
      commit messages.

Change-Id: I0b2aa17ee41d9c2d6a8d27608c532bd7c9e42f8f