HeadsUpManagerTest: Improve and add test cases

1. Fixes the auto-dismiss tests to account for touch acceptance delay
   and adds a test for touch acceptance delay itself.
2. Adds a test for the auto-dismiss timeout when *not* overridden by the
   AccessibilityManager.
3. Add tests for the auto-dismiss timeout on stickyForSomeTime HUNs.
4. Fixes createStickySbn and createStickyForSomeTimeSbn to match the
   expected state from NotificationManagerService, moves them out of
   AlertingManagerNotificationTest since they're not used in it, and
   fixes a related incorrect test case.
5. Extends the test of removing a HUN before the minimum display time to
   assert that it is removed once the minimum display time has passed.
6. Adds a test that asserts that, once the minimum display time has
   passed, we can remove a HUN immediately.
7. Makes some changes to improve code clarity.

Bug: 286263566
Fixes: 294241624
Fixes: 294242806
Fixes: 294284711
Fixes: 294283040
Test: atest HeadsUpManagerTest
Change-Id: Iba0512ce2b5bcf0b80679271be77159c2880a442