Improve debug / bug report logging for time zones

Pushing the local debug logging responsibility down to SystemTimeZone.
Now that all time zone changes go through system time zone, it makes
sense that the logging is moved there. This means that changes for any
reason, now including initial device initialization, and API / shell
command calls can be logged, which previously wasn't the case.

Bug: 236612872
Test: build / boot / factory reset / manual inspection of dumpsys
Test: treehugger
Change-Id: I1e7cf86ae89a73c31e036f68f32f99fae4d6392a