Enable telephony fallback triggered by providers

Now that providers can report their status, we can use this to trigger
telephony fallback mode. This opens the door to more sophisticated
mechanisms for things like flight or tunnel detection. After all,
providers know how they work and what they can / cannot do, and may have
access to sensors and providers that the platform has not.

The new "provider reported" flight mode entry cannot replace the
"time_zone_detector"-level behavior entered via calls to
TimeZoneDetectorStrategy as provider status is new and optional;
providers are not required to report their status so it can be omitted.

Bug: 236624675
Test: atest services/tests/servicestests/src/com/android/server/timezonedetector/
Change-Id: I89fb889ba98b3ddedd271670db09f1bb9df95644