Check if current profile is being removed in IMMS

This adds a check in onUserRemoved inside IMMS, for the userId to be
removed matching currentImeUserId.

If the user is on a work profile app, goes directly to the lock screen
(which is locked with a pattern / pin), and triggers a work profile wipe
due to failed unlock attempt, the currentImeUserId in IMMS will remain
on the now removed work profile, which will essentially block any
further requests to start an input connection. The requests are blocked
in startInputOrWindowGainedFocus, as the passed in userId will not be
one of the profiles associated with the currentImeUserId (as this was
removed, so it won't have any profiles).

This still passes in the majority of the cases as we reach the check
mentioned above before the currentImeUserId is fully removed from
UserManager.

If the currentImeUserId is being removed, we can simply fall back to the
currentUserId of ActivityManager, which is a non-profile user. The only
case where the currentImeUserId can be the one being removed is when it
is actually a profile user. When a non-profile user is the current user,
it cannot be removed, so it would require switching to a different
non-profile user, which we handle in onUserSwitched already. Falling
back to the current non-profile user will recover gracefully in all
situations, as we allow starting input on any profile of
currentImeUserId.

Flag: EXEMPT bugfix
Bug: 341078907
Test: MultiUserMockImeTest#testRemoveCurrentProfileCanStartInputOnOtherUser
Change-Id: I0d22aae115705381f5f74dfd4cf878443eef6027