storage: introduce CasManager to support chunk dedup at runtime #3234

Job	Run time
contrib-build (amd64)	33s
contrib-lint (contrib/nydusify)	1m 0s
contrib-build (arm64)	42s
nydus-build (amd64)	3m 19s
contrib-lint (contrib/nydus-overlayfs)	22s
contrib-unit-test-coverage	20s
contrib-build (ppc64le)	40s
nydus-build (arm64)	3m 47s
contrib-build (riscv64)	39s
nydus-build (ppc64le)	3m 14s
cargo-deny	42s
nydus-build (riscv64)	3m 9s
nydusd-build-macos (amd64)	4m 54s
nydusd-build-macos (arm64)	4m 8s
nydus-unit-test	4m 55s
nydus-unit-test-coverage	4m 5s
nydus-integration-test	11m 30s
takeover-test	1m 59s
performance-test (fs-version-5)	1m 48s
performance-test (fs-version-6)	1m 54s
performance-test (zran)	2m 1s
upload-coverage-to-codecov	9s
	55m 50s

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