Java code for mainline modules to log to statsd.

Adds support for generating app code to allow java mainline modules to
call the StatsLog.writeRaw public API. Supports primitives, enums,
attribution chains, MODE_BYTES. Does not support key value pairs,
worksource methods (because worksource uses hidden apis in the
worksource object).

Test: manually tested atom logging from DocumentsUI
Test: existing autogenerated code is not modified
Test: cts will follow
Bug: 126134616

Change-Id: Ia321cf2d9952e3875ed0c7a28db1f4113711513f