Add test for background playback from inactive media session.

Changes in this CL adds a test case to test if background playback from
inactive media playback service tranistions to foreground state. Test
case intentionally sets various timeout to avoid temporaray bg->fgs
registriction accidentally allowing service transistion to fgs.

Test: atest CtsAppFgsTestCases
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerNotifyMediaFGSTypeTest.java;
Flag: com.android.media.flags.enable_notifying_activity_manager_with_media_session_status_change
Bug: 383481936,281762171

Change-Id: I4f8d4eaea684fc3a68cf0d530a089811985067eb
Signed-off-by: Pradeep Sawlani <sawlani@google.com>