[le audio] Updating broadcast metadata triggers callback

Currently app didn't receive callback as expected upon updating broadcast annoucement.
When native layer updates the broadcast metadata, it should trigger
callback and notify the Java/App layers.

Bug: 347206874
Bug: 347710374
Test: atest bluetooth_test_gd_unit bluetooth_test_broadcaster_state_machine
Test: manual test with broadcast to confirm metadata is updated
Change-Id: I202a32f8d82a54c397cbc597c10c7d1f85929dde