combine completed filters if a timeout occurs

A user reported that they were woken up from an incoming call even
though their DND settings are set to disallow callers.  Upon inspection,
the DND filter was computed and the caller was silenced BUT another
filter timed out causing the final result to allow the caller.

Now, if the DND filter or any other filter is processed and finished
before the timeout, the fitlers will be combined with the final result.

Flag: com.android.server.telecom.flags.check_completed_filters_on_timeout
Bug:   364871465 (root bug)
Fixes: 364946812 (spun off bug)
Test: com.android.server.telecom.tests.IncomingCallFilterGraphTest
                   #testFilterTimesOutWithDndFilterComputedAlready
Change-Id: I88178b4c5b1e76a2c0108092f52bb6d8ec6884b6