Adds parser for Bmgr backup/restore command's output

The library will be used by BackupService in Android Studio (service responsible for triggering Backup&Restore testing flows within Android Studio IDE) to parse output produced by backup & restore commands through bmgr util.
The parser simplifies the output and provides information about failure with actionable information wherever possible.

The jar artifact created from the build will be added as a prebuilt in Android Studio. Updates to the library will require manually importing the updated jar in Android Studio.

Bug: 392866610
Flag: TEST_ONLY
Test: atest BmgrOutputParserTest
Change-Id: I88578ce15ccd5c406ecaf04bec318a4cd8e9775f