Add RECEIVER_NOT_EXPORTED flag for BiometricDanglingReceiver

In Android U, all receivers registering for non-system broadcasts
are required to include a flag indicating the receiver's exported
state. Apps registering for non-system broadcasts should use the
ContextCompat#registerReceiver APIs with flags.

Fixes: 339811510
Bug: 331804186
Test: lunch sdk_phone64_x86_64-trunk_staging-userdebug; time m -j90; \
emulator -wipe-data -no-snapshot -logcat *:V -logcat-output logcat.txt
Test: m RUN_ERROR_PRONE=true
Test: atest FaceInternalEnumerateClientTest
            FingerprintInternalEnumerateClientTest
	    BiometricDanglingReceiverTest
Flag: NONE
Change-Id: Ie4d438cc76b3bb2fbd39af999332fcd5e4a52427