Add sanity test for grpcio protoc package

templates/tools/dockerfile/test/sanity/Dockerfile.template

tools/distrib/python/bazel_deps.sh

tools/distrib/python/check_grpcio_tools.py

tools/distrib/python/grpcio_tools/.gitignore

tools/distrib/python/grpcio_tools/grpc/__init__.py

tools/distrib/python/grpcio_tools/grpc/protoc/__init__.py

...n/grpcio_tools/grpc/protoc/grpc_python_protoc_compiler.py

...hon/grpcio_tools/grpc/protoc/grpc_python_protoc_plugin.py

tools/distrib/python/grpcio_tools/grpc/protoc/main.h

tools/distrib/python/grpcio_tools/grpc/protoc/protoc.pyx

...distrib/python/grpcio_tools/grpc/protoc/protoc_plugin.pyx

tools/distrib/python/grpcio_tools/protoc_deps.py

tools/distrib/python/grpcio_tools/protoc_lib_deps.py

tools/distrib/python/grpcio_tools/setup.py

tools/distrib/python/make_grpcio_tools.py

tools/dockerfile/bazel/Dockerfile

tools/dockerfile/test/sanity/Dockerfile

tools/run_tests/sanity/sanity_tests.yaml