ASM - Bug fixes for clearTopIfNeeded

This includes the following changes:

1. activity starts with UID 0 could fail - they do not have a
   corresponding packageName, resulting in a NPE in the feature flag
   allowlist. We now both explicitely allow UID 0, and check for nulls.

2. We no longer exclude finishing activities in the check. While this is
   generally a no-op, it resulted in noisy logs/toasts. E.G, an activity
   finishes itself and launches a new one with NEW_TASK at the same time
   would result in clearTop being called, even though there is nothing
   to clear.

   This is net-neutral for security - the finishing activity could have
   already morphed itself rather than finishing.

3. We move the home task to front of the finishing tas in
   checkActivitySecurityForTaskClear, rather than to front of display
   area. For multi-window scenarios, this could result in one app
   forcing a home switch for the other.

4. Allow launches from top of stack, even if finishing or alwaysOnTop.
   This supports tasks which are always set to alwaysOnTop, if they try
   to start or finish activities

Bug: 271417931
Test: ABTD with all WM tests and InputMethod tests
Change-Id: I966319723b17f1affd92e141791596e5da644050