General improvements / refactoring

Fix documentation, command line formatting and improve logging. No
functional changes.

To improve logging, the refreshIfRequiredAndReschedule() method has been
renamed to refreshAndRescheduleIfRequired() (because it now may not
reschedule) and it can now accept a null Network parameter to log the
case that was previously handled in the untested code. Tests have been
updated accordingly.

Test: manual / treehugger
Test: atest services/tests/servicestests/src/com/android/server/timedetector/NetworkTimeUpdateServiceTest.java
Bug: 269425914
Change-Id: Ib54da77d85ae0949b560b22659263f4f13f7a61e