Various tidy ups / refactoring

Rename the TimeDetectorService / TimeZoneDetectorService "Callback"
interface "Environment", since "Callback" causes confusion.

Correct the docs for TimeZoneDetectorService, which had fallen out of
date.

Tidy up log tags - make them more consistent / shorter.

Tidy up the naming for the boolean that records whether the location
time zone detection feature is enabled on a device: now called
"supported" in code, since "enabled" could be confused with the user's
setting to enable it.

Test: treehugger
Bug: 149014708
Change-Id: Ia6f8fe971f68ef4660b41b66941320c3fc118917