refactor: make crane write blobs to disk #1006

Job	Run time
test-auth	1m 50s
matrix-prep-os	1s
matrix-prep-bazelversion	3s
test (ubuntu-latest, 6.2.0, ., true)	2m 34s
test (ubuntu-latest, 6.2.0, ., false)	4m 16s
test (ubuntu-latest, 6.2.0, e2e/custom_registry, false)	1m 13s
test (ubuntu-latest, 6.2.0, e2e/wasm, false)	35s
test (ubuntu-latest, 6.2.0, e2e/smoke, true)	20s
test (ubuntu-latest, 6.2.0, e2e/smoke, false)	19s
test (ubuntu-latest, 6.2.0, e2e/crane_as_registry, true)	16s
test (ubuntu-latest, 6.2.0, e2e/crane_as_registry, false)	12s
test (ubuntu-latest, 5.3.2, ., false)	2m 12s
test (ubuntu-latest, 5.3.2, e2e/custom_registry, false)	55s
test (ubuntu-latest, 5.3.2, e2e/wasm, false)	1m 4s
test (ubuntu-latest, 5.3.2, e2e/smoke, false)	20s
test (ubuntu-latest, 5.3.2, e2e/crane_as_registry, false)	21s
test (macos-latest, 6.2.0, ., true)	11m 14s
test (macos-latest, 6.2.0, ., false)	5m 47s
test (macos-latest, 6.2.0, e2e/smoke, true)	1m 8s
test (macos-latest, 6.2.0, e2e/smoke, false)	53s
	35m 33s

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