Introduce MultiPriorityQueue

ACL and L2cap needs to prioritize some link/channels in some cases.  A
traditional priority queue requires predefined comparison, which can be
hard for our use case (PacketBuilder).  Instead, we specify the priority
value when we push to a queue.

Test: bluetooth_test_gd
Tag: #gd-refactor
Bug: 141555841
Change-Id: I33414b4bf81e9f63c88d8627376b565f5c5bb6de