Fix and rewrite hearing device summary with battery info

*The TV summary with hearing device logic is skipped unexpectedly in the current
implementation.
* Rewrite the hearing device summary logic to make it more readable.

Bug: 307705966
Test: atest CachedBluetoothDeviceTest
Flag: EXEMPT bugfix

Change-Id: I8fa829edcadddf140769260adb9557a56598cca9