Add tests for BR/EDR temp bond authentication

As an action item following a regression postmortem, we need to create
tests covering the behavior when accessing a secure service from a temp
bond.  This is an internal function and is not directly accessible to
unit testing, but can be accessed via several indirect entry points.

Three tests have been added to cover different scenarios, all using
btm_sec_mx_access_request as the entry point.

Bug: 333617609
Test: atest StackBtmSecWithInitFreeTest
Tag: #security
Flag: EXEMPT test_only
Merged-In: I5183ea06c1a5b3f878b8a1ad648caba666c46981
Change-Id: I5183ea06c1a5b3f878b8a1ad648caba666c46981