storage: introduce CasManager to support chunk dedup at runtime #3209

Job	Run time
contrib-build (amd64)	39s
contrib-build (arm64)	49s
contrib-unit-test-coverage	24s
contrib-build (ppc64le)	46s
contrib-lint (contrib/nydusify)	57s
contrib-build (riscv64)	45s
contrib-lint (contrib/ctr-remote)	45s
nydus-build (amd64)	2m 10s
cargo-deny	37s
contrib-lint (contrib/nydus-overlayfs)	26s
nydus-build (arm64)	2m 11s
nydusd-build-macos (amd64)	2m 31s
nydusd-build-macos (arm64)	2m 29s
nydus-unit-test-coverage	3m 53s
nydus-build (ppc64le)	2m 17s
nydus-build (riscv64)	2m 1s
nydus-unit-test	4m 51s
performance-test (fs-version-5)	1m 20s
nydus-integration-test	6m 27s
takeover-test	1m 31s
performance-test (fs-version-6)	1m 9s
performance-test (zran)	1m 26s
upload-coverage-to-codecov	8s
	40m 32s

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