Add support for tz detection telephony fallback

This adds support for a telephony fallback mode used when geolocation
time zone detection is enabled. Before this change, when geolocation tz
detection mode was enabled only geolocation signals were used. To
improve behavior when geolocation detection doesn't work or is slow
after a flight (or immediately after boot), this "latched" fallback mode
allows telephony suggestions to be used until the geolocation algorithm
makes a "certain" suggestion. See more TimeZoneDetectorStrategy for more
information.

The "flight detection" is entirely based on the user switching off
airplane mode in this version.

Bug: 197624972
Test: atest services/tests/servicestests/src/com/android/server/timezonedetector/
Change-Id: Id72108c6ccb273fb8b7dd52847e2a750cd0a676a