Rename, refactor, & basic caching. #160

Job	Run time
prepare	1s
test / prepare	5m 34s
test / run (containerd, ./frontend/dockerfile, integration)	4m 59s
test / run (containerd, ./frontend/dockerfile, dockerfile)	4m 2s
test / run (containerd-rootless, ./frontend/dockerfile, integration)	3m 17s
test / run (containerd-rootless, ./frontend/dockerfile, dockerfile)	4m 17s
test / run (containerd-1.6, ./frontend/dockerfile, integration)	3m 45s
test / run (containerd-1.6, ./frontend/dockerfile, dockerfile)	4m 32s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, integration)	3m 32s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	4m 35s
test / run (oci, ./frontend/dockerfile, integration)	3m 29s
test / run (oci, ./frontend/dockerfile, dockerfile)	3m 40s
test / run (oci-rootless, ./frontend/dockerfile, integration)	3m 14s
test / run (oci-rootless, ./frontend/dockerfile, dockerfile)	3m 48s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, integration)	3m 22s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	3m 39s
image	0s
release	0s
	59m 46s

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