Floss: print log on A2DP audio state update

Sometimes the transition time of the audio state provides great clue for
the root cause of certain race issues (e.g., controller responds to
start/suspend too slowly).

This CL allows A2DP to log audio state updates similar to how HFP
logs its audio states.

Bug: 333619168
Test: m Bluetooth
Flag: EXEMPT floss only changes
Change-Id: I0b0f957151976ebb02766c0c0cd316b7d6cb1ba0