[DO NOT MERGE] Check caller's uid in backupAgentCreated callback

AM.backupAgentCreated() should enforce that caller belongs the package called in the API.

Bug: 289549315
Test: atest android.security.cts.ActivityManagerTest#testActivityManager_backupAgentCreated_rejectIfCallerUidNotEqualsPackageUid
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ebdcc72a235d6b2a65e1d1c99d7a9eb89f309357)
Merged-In: I9f3ae5ec0b8f00e020d471cc0eddf8bd8bdbb82d
Change-Id: I9f3ae5ec0b8f00e020d471cc0eddf8bd8bdbb82d