Adding privacy tags to graphicsstats proto.

Creating a copy of the graphicsstats proto so that one can be tagged
with privacy annotations and the other can be used internally while
still using the protobuf-cpp-lite library.

This is the same change as the pi-dev one (http://ag/3841646), but due
to changes in master, that change has a merge conflict, so I have to
create a separate CL for master.

Bug: 72570104
Test: it builds
Change-Id: I2d72e7bd17689c1401a16d5a13956e6528ddb525