Add `cvd cache` #466

Job	Run time
build-metapackage-deb-job	7m 20s
build-installer-iso-job	2m 36s
build-uboot-qemu-job	3m 26s
build-cuttlefish-deb-job / build-arm64-cuttlefish-deb-job	1h 50m 30s
test-install-metapackage-deb-job	9m 25s
test-install-cuttlefish-deb-job	9m 27s
	2h 22m 44s

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