AVRCP Browsing concurrency

When performing browsing commands allow other commands that can be
processed simultaneously to execute.  Update states that extend
CmdStgate to pass those messages up to the parent connected state for
processing.

Bug: 72495854
Test: runtest bluetooth
Change-Id: I2e1073a7d3befaf3a263b2d10f8b571f78d66cf6
(cherry picked from commit 2144382a)