Adjust OWNERS to reflect new ownership

This changes owners files based on latest org changes and changes
links to improve maintainability.

Changes:
+ It removes a specific owner from most to reduce future maintenance.
+ It adds indirection so android/app references the associated service
code, tests reference the OWNERS of the code under test.
+ services/core/java/com/android/server/timezonedetector/OWNERS is the
single list of time / time zone detector maintainers.
+ Code associated with time zone rules moved to libcore/ ownership
+ It adds one new file for an upcoming commit.
+ Added documentation around API purpose to API OWNERS files, since
there are multiple similar-looking package names with different purposes
/ clients.

Test: None
Bug: 189810551
Change-Id: I948d4b8eff59f3cd5ff63018949e49679795a5c0