Add UnsupportedAppUsage annotation to core platform and intra core apis

Needed for conscrypt, bouncycastle and other consumers of the two APIs.

There appears to be a bug in metalava (http://b/119398397) as the
UnsupportedAppUsage methods are not listed in the .txt files even
though they are annotated with @CorePlatformApi and @IntraCoreApi. They
are present in the stubs though.

Bug: 117818301
Bug: 119398397
Test: make checkbuild
Change-Id: I53c7ff712653aa6102cb24d5655dc0b9b60660e1
3 files changed