Add tuner session and conversion utils unit tests

Added missing unit tests for tuner session and methods related to
HAL result conversion, radio metadata, vendor key/value parameters
and related contents in broadcast radio service.

Bug: 282031772
Test: atest BroadcastRadioTests
Flag: TEST_ONLY
Change-Id: I88353fe91eb253c31eecd6be311cccfea021f13a