2nd attempt to fix Slice strict mode.

1. Use real BluetoothAdapter instead of settingslib version. The
   settingslib version contains calls that violates strictmode rules.
2. Override StrictMode rules in SettingsSliceProvider when it's called
   in background thread. When in background, the enforcement from Slice
   framework (StrictMode#ThreadPolicy) is not useful and can be safely
   ignored.

Change-Id: I68523148f4c1dc88a54e207447d21ec439478cdf
Bug: 79985175
Test: robotests