tests: Multiple unit test fixes

This fixes failed mocking, unsupported class loader errors
and improves tests stability.

Bug: 230559809
Tag: #feature
Sponsor: jpawlowski@
Test: atest BluetoothInstrumentationTests
Change-Id: I5953c49bb11af13fe9578be709f02582080124f3
Merged-In: I5953c49bb11af13fe9578be709f02582080124f3
(cherry picked from commit 8071a43a)