Add a manual path for setting time zone

Add a mechanism for suggesting the "manual" time zone setting to the
TimeZoneDetectorStrategy, e.g. for the settings app to use. This
involves various changes / renames to TimeZoneDetectorStrategy to
introduce a distinction between 3 things:
1) General detection code, applicable for anything that changes device
time zone.
2) Phone detection code, applicable for setting the device time zone
from phone signals.
3) Automatic detection code, applicable for setting the device time zone
automatically (of which telephony signals is currently the only example,
but could be joined by new things in future).

Adds tests for the new ManualTimeZoneSuggestion and makes improvements
to the existing tests for PhoneTimeZoneSuggestionTest.

Test: atest android.app.timezonedetector
Test: atest com.android.server.timezonedetector
Bug: 140712361
Change-Id: I9c3a18e47b157cccabda74855e5c91b45fa93b92