[AI TestGen]

Test: Add test for bubble bar overflow expanded view

Adds a unit test to verify that when the BubbleBarExpandedView is
initialized for the overflow state, the caption and handle views are
hidden.


This change adds additional test coverage for based on change: ag/34451416
Target source file: libs/WindowManager/Shell/src/com/android/wm/shell/bubbles/bar/BubbleBarExpandedView.java.


Flag: TEST_ONLY
Test: atest libs/WindowManager/Shell/multivalentTests/src/com/android/wm/shell/bubbles/bar/BubbleBarExpandedViewTest.kt (passed locally)
Bug: 431235865

Change-Id: I1aff1550eabca61ab243457f186f3b30e1f5ac9e