Upgrade to grpc-1.42.0

[rkaippully]

• Upgraded the pinned nixpkgs to nixos-21.11 which contains grpc-1.42.0. This requires no code changes to grpc-haskell and grpc-haskell-core libraries.
• Picked up latest commits of proto3-{wire,suite} and adjusted transitive dependencies
• Switched to python 3 because grpcio-tools requires it. Adjusted test scripts accordingly.
• Upgraded to latest CI action versions.

This change is minimal compared to #138 and will solve some test failures in that PR. Hopefully, this will make it easier to move that PR forward.