Re-organize the Perfetto BUILD file.
Re-organize the Perfetto BUILD file.

 - Put in some higher-level sorting with group markers
 - Keep proto rules together with their language specific generators

google/gapid,pmuetschard/gapid,google/agi,pmuetschard/gapid,pmuetschard/gapid,google/agi,pmuetschard/gapid,google/gapid,google/gapid,pmuetschard/gapid,google/agi,google/gapid,google/agi,pmuetschard/gapid,google/agi,google/agi,google/gapid,google/gapid,google/agi,google/gapid,google/gapid,pmuetschard/gapid,pmuetschard/gapid,google/agi