Add test for focal area collection on finished transition to lockscreen

Adds a unit test to verify the behavior of the `shouldCollectFocalArea` flow when the SceneContainer flag is disabled.

The new test, `shouldCollectFocalArea_whenTransitioningToLockscreen_sceneContainerDisabled`, ensures that focal area collection is correctly triggered during the full lifecycle of a transition to the lockscreen, specifically verifying that collection continues after the transition has finished. This covers the logic recently added to the `merge` operator.


Please help fill out the survey for feedback: https://docs.google.com/forms/d/e/1FAIpQLSeKFKpHImCAqZIa_OR801cw72HQUreM2oGM25C3mKKT2tBFnw/viewform?usp=pp_url&entry.1586624956=ag/35508205

Please feel free to make changes to the generated tests based on your domain knowledge. More context about the project please see go/ai-testgen

Original Change: ag/35313430 (Note tests are based on the original CL but may add coverage beyond the specific changes to improve overall code health)

Test: http://ab/I55300010444928321 (with ag/35313430 reverted, failing) vs. http://ab/I99900010444710020 (with ag/35313430 in the code base, passing),  AND ATP tests passed http://go/forrest-run/L97800030017698431
Bug: 431235865
Flag: TEST_ONLY



Change-Id: I33268616d55612aa80063c53858e79fb740b53b6