test: allow testing frontends from different version #5046

Job	Run time
prepare	1s
test / prepare	2m 21s
test / run (containerd, ./frontend/dockerfile, integration)	4m 56s
test / run (containerd, ./frontend/dockerfile, dockerfile)	6m 47s
test / run (containerd-rootless, ./frontend/dockerfile, integration)	4m 50s
test / run (containerd-rootless, ./frontend/dockerfile, dockerfile)	6m 34s
test / run (containerd-1.6, ./frontend/dockerfile, integration)	5m 12s
test / run (containerd-1.6, ./frontend/dockerfile, dockerfile)	7m 25s
test / run (containerd-1.7, ./frontend/dockerfile, integration)	5m 19s
test / run (containerd-1.7, ./frontend/dockerfile, dockerfile)	7m 16s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, integration)	5m 23s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	7m 26s
test / run (oci, ./frontend/dockerfile, integration)	4m 19s
test / run (oci, ./frontend/dockerfile, dockerfile)	6m 0s
test / run (oci-rootless, ./frontend/dockerfile, integration)	4m 31s
test / run (oci-rootless, ./frontend/dockerfile, dockerfile)	5m 52s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, integration)	4m 27s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, dockerfile)	6m 12s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, integration)	4m 22s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	5m 52s
image (mainline)	5m 16s
image (labs)	5m 1s
release	0s
scout	0s
	1h 55m 22s

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