Add test for transitions between non-dual shade modes

Adds a unit test to verify that when the shade mode changes between different non-dual modes (e.g., from Single to Split and back), the scene correctly remains on the Shade scene.

This covers a scenario mentioned in the related change, improving test coverage for device configuration changes like rotations that can trigger shade mode transitions.


Please help fill out the survey for feedback: https://docs.google.com/forms/d/e/1FAIpQLSeKFKpHImCAqZIa_OR801cw72HQUreM2oGM25C3mKKT2tBFnw/viewform?usp=pp_url&entry.1586624956=ag/35405901

Please feel free to use your domain knowledge to make changes to the generated tests to make it more valuable for your team.
Original Change: ag/34973966
Test: ATP tests passed http://go/forrest-run/L60400030017375431
Bug: 431235865
Flag: TEST_ONLY



Change-Id: If0792d21ebe67c10bce056c5521598915a0fc76f