APM: Add a test to prevent regressions like one from aosp/3020124

Retroactively add an APM unit test that would have prevented
the regression caused by strategies reordering by aosp/3020124.

Tested by re-applying broken strategies order and checking that
the test is failing in this case.

Flag: EXEMPT bugfix
Bug: 376030167
Test: atest audiopolicy_tests
Change-Id: Iebd26509a57cfc3b11a2d9c87e687588c133903d