Fix some C# copyrights

Added missing codegen includes

Change the census metadata keys.

Drop Python interop tests' "make install-certs"

Fix Profilers for coreclr

grpc_set_ssl_roots_override_callback for Python.

Refactor dockerfiles

Flagging master's version properly.

Fix csharp environment test

Enable Node distrib tests on Mac

Fix C# build

Make Node's package.json use the version from build.yaml