Separate battey levels for dual mode devices

Dual mode devices can notify the battey level in two paths:
one from HFP and one from the battery service.

This change separates the two battery levels so that the
battery level is not reset when one of two profiles is
diconnected.

Bug: 287375627
Test: atest BluetoothInstrumentationTests
Change-Id: Ie714490e39ea4b6911d40369ab85f9eb8a6eb468