Add a mechanism to dump A2DP codec stats

Also, added-back A2DP SBC frames related stats:
  - media_read_total_limited_frames
  - media_read_max_limited_frames
  - media_read_limited_count
  - media_read_total_expected_frames
  - media_read_max_expected_frames
  - media_read_expected_count

A2DP SBC State:
  Frames expected (total/max/ave)                         : 9131 / 8 / 6
  Frames limited (total/max/ave)                          : 0 / 0 / 0
  Counts (expected/limited)                               : 1322 / 0

Bug: 30958229
Test: manual
Change-Id: Id6ddea5eb9d39cf03cae84c79968081d56984e91