* Rename nanopb/.../*.pb.c to nanopb/.../*.nanopb.c
This ensures that all generated nanopb files use the same (sub)
extension of nanopb. This matches up with nanopb's --extension
parameter (which will be enabled later in this PR.)
* Remove references to NANOPB_PROTOC_BIN
Which wasn't being used, and wasn't pointing to a valid protoc.
* Add ability to generate protos from cmake build.
Currently, it's an entirely manual process via 'generate_protos' target.
This target is not automatically run during a build.
See Firestore/Protos/build-protos.sh for expected usage.
* cleanup/update license in build-protos.sh
* Build grpc proto sources (objc only)
* Use 32bit nanopb fields (instead of 16)
To match xcode build, but also to allow google/api/annotations.proto to
compile. (A recent change to nanopb now enforces this.) This isn't
strictly necessary, since we don't make use of that proto, so we
could've simply removed it instead (and in fact, the objc protos do
exactly that) but matching the xcode build certainly seems worthwhile.
* Rebuild all proto sources
* Skip whitespace checks on protoc generated files
Previously, the tests would compare serialization results against a
precomputed (via protoc) array of bytes. Now they serialize via our
nanopb based class and deserialize via libprotobuf (and vice versa) and
then ensure the result is the same as the input
rsgowman