Add test for quick switch animation race condition

Adds a new unit test to verify that the expanded view's visibility is correctly set to VISIBLE at the start of a switch-in animation.

This test simulates a race condition that can occur during a rapid switch between bubbles (e.g., A -> B -> A). It ensures that even if the "switch out" animation for a bubble (A) finishes late and sets its visibility to INVISIBLE, the subsequent "switch in" animation for that same bubble will correctly restore its visibility to VISIBLE, preventing the bubble from disappearing.

Original Change: ag/34894797 (Note tests are based on the original CL but may add coverage beyond the specific changes to improve overall code health)

Please help fill out the survey for feedback: https://docs.google.com/forms/d/e/1FAIpQLSeKFKpHImCAqZIa_OR801cw72HQUreM2oGM25C3mKKT2tBFnw/viewform?usp=pp_url&entry.1586624956=ag/35413245

Please feel free to use your domain knowledge to make changes to the generated tests to make it more valuable for your team.

Test: Without original one-line fix (http://ab/I23600010441008136), With original one-line fix (http://ab/I73200010442187511) AND ATP tests passed http://go/forrest-run/L63600030017457342
Bug: 431235865
Flag: TEST_ONLY

Change-Id: I8fbc0769e00d9cc2be9433e4d64d4f3ebcafecbb