Set the A2DP media channel as a high priority L2CAP link

Use dynamic ACL buffer allocation for high priority links:
1. Ensure dedicated ACL buffers for high priority links
2. Adjust buffer allocation if the priority of the link changes

Test: Manually tested with 4 HID devices and A2DP streaming scenario
Bug: 30787081
Change-Id: Id3c4a76e360aee322e9f8073bd399807e7987990
(cherry picked from commit 624ba681a63fa5ecf778b0b019735359654c6dd0)