Add a function to Dumpstate service to trigger a bugreport

Add startBugreport() to Dumpstate interface. This is part of
proper binderization of Dumpstate.

The function is not implemented yet.

BUG: 111441001
Test: m -j dumpstate
Test: adb shell /data/nativetest64/dumpstate_test/dumpstate_test
Change-Id: I484215067e5653d2e2f4e34bd9a9b569d426f411