Show only 1 entry for hearing aid device after killing the activity.

This CL detects Bluetooth hearing aid devices and tries to
combine the entry of the hearing aids with the same HiSyncIds and
shows only 1 entry for each pair in the connected devices list. This CL
works for scenarios just after pairing and reopening settings
activity after killing it.

This CL also has the logic to combine the entries just after pairing and
to forget both the devices on pressing forget for the combined entry.

Test: RunSettingsLibRoboTests
Bug: 74204427
Change-Id: Ib4c76eb0cae12937dd8403e37a0af8297a4aedc2