Add metadata to save ACTION_KEY_MISSING intent count

Add get/updateKeyMissingCount() APIs for BluetoothDevice.
This allows 1P apps to get/update key missing count for a BluetoothDevice. The key missing count is persisted in the Metadata database.

Change-Id: I6ec8c4921547850ed7188b6862e1fe99a46c8be6
Flag: EXEMPT adding metadata
Test: m com.android.btservices
Test: m statsd_testdrive
Test: m statsd_testdrive -terse 390
Test: atest DatabaseManagerTest BluetoothDeviceTest
Bug: 394650229