ProtoLog: Cache the result of ProtoLogImpl.isEnabled(ProtoLogGroup)

We introduce a generated class ProtoLog$Cache, which contains a field
for each ProtoLogGroup to cache whether it is enabled or not.

This both makes lookup faster, and reduces code size.

Test: make droid
Change-Id: I581c87849c875918b182eff85996b6d19a6755ec
8 files changed