Sort out codegen dependencies

BUILD

Makefile

binding.gyp

build.yaml

config.m4

gRPC.podspec

grpc.gemspec

package.json

package.xml

src/python/grpcio/grpc_core_dependencies.py

tools/buildgen/plugins/expand_filegroups.py

tools/doxygen/Doxyfile.c++

tools/doxygen/Doxyfile.c++.internal

tools/doxygen/Doxyfile.core

tools/doxygen/Doxyfile.core.internal

tools/run_tests/sources_and_headers.json

vsprojects/buildtests_c.sln

vsprojects/grpc.sln

vsprojects/grpc_csharp_ext.sln

vsprojects/grpc_protoc_plugins.sln