Clean up reflection-related services keep rules

Prefer using annotations (@UsesReflection + @UsedByReflection) for
various classes that are instantiated via reflection in system server.
The auto-generated keep rules are comparable to the existing ones, but
are easier to maintain and more targeted.

Test: m + diff services.jar for equivalent output
Bug: 210510433
Change-Id: I306b4533f723ee7fafba1de12d7fe446544f8ce7