Adapter: static cache for getState

Since:
* getState does not requires any permission
* has only one unique and identique value for the whole system

Then I believe we do not need to pass any parameter to the cache and we
also do not need to cache multiples entries

Bug: 374222784
Bug: 362569584
Flag: com.android.bluetooth.flags.get_state_from_system_server
Test: m .
Change-Id: I692f62675f3d90d6446ced8e8e29e12f51ba692f