BtaAvCo Peer 's add, read, update operations to its own class.

Problem: Currently, BtaAvCo class is responsible to add update
peers.

Solution: Refactor the responsibility to a separate class.

Bug: 326504354
Test: m seahawk-trunk-userdebug
Test: atest net_bt_*
Flag: EXEMPT. no logical change, refactor to a new class.
Change-Id: I9eddf4d4d9b718c02b56a34cfe0548f377a97f5a