[le audio] BassClient enhancement to allow re-sync with known inactive source

In current design, assistant will not be able to add source for inactive source. This commit implemented a solution to allow re-sync to previously cached source.

When syncing with a new source, the assistant will cache the scan result. Then if later the device stoped the sync or user chose to remove the source, adding source operation will check the previous cached scan results. If the source has been found, the assistant will try to resync to this known remote source.

No need to clean up the cached broadcast when stopping the scan since
starting scan will do the cleanup.

Bug: 299422016
Test: atest BassClientStateMachineTest
Test: manual test with broadcast

Change-Id: I09f0c261fd5c937fca75f84046199d6aa6d2c768