Support OS version in platform string #5197

Job	Run time
prepare	1s
test / prepare	2m 56s
test / run (containerd, ./frontend/dockerfile, integration)	9m 2s
test / run (containerd, ./frontend/dockerfile, dockerfile)	14m 8s
test / run (containerd-rootless, ./frontend/dockerfile, integration)	8m 59s
test / run (containerd-rootless, ./frontend/dockerfile, dockerfile)	14m 22s
test / run (containerd-1.6, ./frontend/dockerfile, integration)	23m 14s
test / run (containerd-1.6, ./frontend/dockerfile, dockerfile)	14m 51s
test / run (containerd-1.7, ./frontend/dockerfile, integration)	8m 56s
test / run (containerd-1.7, ./frontend/dockerfile, dockerfile)	14m 13s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, integration)	9m 24s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	20m 30s
test / run (oci, ./frontend/dockerfile, integration)	9m 41s
test / run (oci, ./frontend/dockerfile, dockerfile)	13m 53s
test / run (oci-rootless, ./frontend/dockerfile, integration)	8m 28s
test / run (oci-rootless, ./frontend/dockerfile, dockerfile)	18m 9s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, integration)	9m 0s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, dockerfile)	13m 58s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, integration)	8m 30s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	19m 26s
image	0s
scout	0s
release	0s
	4h 1m 41s

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