protobuf: add vtproto as a supplemental marshaler #4977

Job	Run time
govulncheck	58s
prepare	4s
binaries (darwin/amd64)	59s
binaries (darwin/arm64)	1m 13s
binaries (linux/amd64)	2m 9s
binaries (linux/arm/v7)	2m 8s
binaries (linux/arm64)	2m 8s
binaries (linux/s390x)	2m 11s
binaries (linux/ppc64le)	1m 56s
binaries (linux/riscv64)	2m 0s
binaries (windows/amd64)	1m 38s
binaries (windows/arm64)	1m 40s
test / prepare	2m 4s
test / run (containerd, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	8m 25s
test / run (containerd-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integr...	9m 30s
test / run (containerd-1.6, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	8m 3s
test / run (containerd-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./fronte...	8m 43s
test / run (oci, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	5m 4s
test / run (oci-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	5m 0s
test / run (oci-rootless-slirp4netns-detachnetns, ./client ./cmd/buildctl ./worker/containerd ./solver ....	5m 39s
test / run (oci-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, int...	5m 12s
test / run (./..., 1, integration gateway)	4m 12s
test / run (./client, containerd, nydus, integration)	7m 25s
test / run (./client, oci, nydus, integration)	5m 1s
test / run (./..., nydus, 1, integration)	4m 12s
image	49s
image (rootless)	49s
release	1s
scout	1s
	1h 39m 14s

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