[le audio] Support rolling window sync for extra remote sources

In current design, we're skipping the extra source when the device hit
max limit.

This commit improved this part by removing one synced source first and
then proceed with syncing. considering we've cached the scan result in
previous changes, the device could allow more than limit sources to be
synced.

Bug: 298662882
Test: atest BassClientServiceTest BassClientStateMachineTest
Test: manual test with broadcast
Change-Id: I29177e20feb071cccc198b9279f155870a376dd6