Support OS version in platform string #5198

Job	Run time
prepare	1s
test / prepare	1m 58s
test / run (containerd, ./frontend/dockerfile, integration)	7m 17s
test / run (containerd, ./frontend/dockerfile, dockerfile)	6m 6s
test / run (containerd-rootless, ./frontend/dockerfile, integration)	5m 31s
test / run (containerd-rootless, ./frontend/dockerfile, dockerfile)	6m 15s
test / run (containerd-1.6, ./frontend/dockerfile, integration)	5m 25s
test / run (containerd-1.6, ./frontend/dockerfile, dockerfile)	5m 35s
test / run (containerd-1.7, ./frontend/dockerfile, integration)	5m 32s
test / run (containerd-1.7, ./frontend/dockerfile, dockerfile)	5m 34s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, integration)	5m 43s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	6m 42s
test / run (oci, ./frontend/dockerfile, integration)	4m 55s
test / run (oci, ./frontend/dockerfile, dockerfile)	5m 3s
test / run (oci-rootless, ./frontend/dockerfile, integration)	5m 12s
test / run (oci-rootless, ./frontend/dockerfile, dockerfile)	5m 13s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, integration)	5m 3s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, dockerfile)	5m 29s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, integration)	5m 1s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	5m 0s
image	0s
scout	0s
release	0s
	1h 42m 35s

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