Make manual suggestions synchronous/return result

Modify the suggestManual...() methods on TimeDetector and
TimeZoneDetector to be synchronous, and have them return true/false to
indicate if the call "succeeded". This is being done before adding more
calls that will be used by apps like SettingsUI; generally all calls
that are user facing and could conceivably fail should return
success/failure information and therefore need to happen synchronously.

Test: atest services/tests/servicestests/src/com/android/server/timedetector/
Test: atest services/tests/servicestests/src/com/android/server/timezonedetector/
Bug: 140712361
Change-Id: I5b6b7fb5af2ffe88392b2ca8d1e8fff2a187521b