Refactor: if `storage-v2` enabled, deprecated `RaftStorage` #3123

Job	Run time
external-stores (stores/rocksstore-v2)	6m 2s
cluster-benchmark (cluster_benchmark)	49s
examples (stable, raft-kv-memstore)	2m 11s
examples (stable, raft-kv-memstore-generic-snapshot-data)	55s
lint	6m 23s
openraft-feature-test (nightly)	47s
examples (stable, raft-kv-memstore-singlethreaded)	1m 15s
openraft-feature-test (nightly, serde)	49s
examples (stable, raft-kv-rocksdb)	6m 31s
examples (nightly, raft-kv-memstore)	2m 8s
openraft-test (stable, 0)	2m 52s
openraft-feature-test (nightly, single-term-leader)	48s
openraft-test (nightly, 30)	3m 16s
examples (nightly, raft-kv-memstore-generic-snapshot-data)	1m 17s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	49s
openraft-test (nightly, 0, single-term-leader)	3m 4s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 18s
examples (nightly, raft-kv-rocksdb)	11m 45s
openraft-test-bench (nightly)	52s
stores (memstore)	55s
stores (rocksstore)	6m 7s
Build (nightly, bench,serde,bt,singlethreaded)	50s
stores (rocksstore-compat07)	6m 13s
tests-feature-test (nightly)	2m 47s
stores (sledstore)	1m 13s
tests-feature-test (nightly, single-term-leader)	2m 50s
tests-feature-test (nightly, loosen-follower-log-revert)	2m 52s
	1h 17m 38s

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