Add test to verify transient launch with keyguard

To simulate the case: a show-when-locked activity occluded
keyguard. Then when using gesture navigation to swipe-up
to trigger a transient transition, both the top app and recent
activity should be collected to transition with change. So
the condition "(mKeyguardLocked && mRecentsTask != null)" in
RecentsTransitionHandler will be satisfied.

Bug: 291123560
Test: atest ActivityStarterTests#testTransientLaunchWithKeyguard
Change-Id: Ie708af9cba9fa934cacad7b8338453da3ec871a3