Refactor bubble lookup and code organization.

This commit refactors the BubbleData and BubbleController classes by
consolidating duplicate bubble lookup logic using predicate, fixing a
typo in a method name, adding final declarations for variables, adding
@NonNull annotations where appropriate, and removing an unused method.

BUG: 387193964
Test: atest SystemUITests:BubblesTest
Test: atest WMShellMultivalentTestsOnDevice
Flag: EXEMPT refactor
Change-Id: I5eb37fcfb4ef655ac7f454d62189a5bf7ac2f7a5