Add schema for task profiles

- Add proto3 files as schema for JSON task profiles / cgroups
  files.

- Add tests to ensure the JSON files (on the device) conforms
  the schema. (libprocessgroup_proto_test)

Test: libprocessgroup_proto_test

Bug: 123664216
Change-Id: I1cab73bd0d3852ff8827fee0be22373da8a6fc5b