Revamp grpc support #999

Job	Run time
check-rust	3m 51s
test-rust (ubuntu-20.04)	27m 56s
test-rust (windows-2022)	44m 3s
test-rust (macos-14)	23m 55s
build-vegafusion-python-linux-64	3m 13s
build-vegafusion-python-linux-arm64	3m 42s
build-vegafusion-python-osx-64	5m 25s
build-vegafusion-python-osx-arm64	2m 55s
build-vegafusion-python-win-64	9m 7s
build-vegafusion-server-linux-64	2m 36s
build-vegafusion-server-win-64	6m 33s
build-vegafusion-wasm	3m 52s
check-vegafusion-python	10m 44s
build-vegafusion-server-linux-arm64	2m 34s
build-vegafusion-server-osx-64	4m 53s
build-vegafusion-server-osx-arm64	2m 42s
test-vegafusion-python-osx-arm64	4m 37s
test-vegafusion-python-linux-64	30m 33s
test-vegafusion-python-win-64	9m 52s
	3h 23m 3s

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