BassClient: State machine cleanup

Remove state machines and cached states for the unbonded devices.
This is preparation for the unit tests in the following patches.

Bug: 239546757
Tag: #feature
Sponsor: jpawlowski@
Test: atest BluetoothInstrumentationTests
Change-Id: I6e68ddb15695f1ea85c6054d0c410225af685e5f