Update SF dump to use proto3

The C++ implementation of Proto2 writes default values to the protobuf object, whenever they are set in the app. That is, if we write 0 into an integer or float field, the protobuf writes the value 0 in the object.

Proto3 skips default values, even if they are set.

Changing from proto2 to proto3 reduces by ~20% the memory requirement for storing SF traces. It also allows default values to be ignored in Winscope

Test: Record a SF trace. Flash a device. Record another SF trace. Check the trace size and/or open them in winscope version with "display defaults" unchecked.
Change-Id: I69ff09d141f6f31f22a4f5fc90bf58cf222d9aae