Refactor: Remove sledstore as a storage backend #4222

Job	Run time
lint	11m 50s
examples (stable, memstore)	35s
openraft-feature-test (nightly)	51s
examples (stable, raft-kv-memstore)	2m 30s
cluster-benchmark (cluster_benchmark)	53s
openraft-feature-test (nightly, serde)	52s
openraft-test (stable, 0)	3m 17s
examples (stable, raft-kv-memstore-network-v2)	47s
openraft-feature-test (nightly, single-term-leader)	50s
openraft-test (nightly, 30)	3m 26s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	49s
examples (stable, raft-kv-memstore-opendal-snapshot-data)	1m 1s
openraft-test-bench (nightly)	57s
openraft-test (nightly, 0, single-term-leader)	3m 14s
examples (stable, raft-kv-memstore-singlethreaded)	50s
rt-monoio	44s
examples (stable, raft-kv-rocksdb)	8m 26s
stores (stores/memstore)	52s
examples (nightly, memstore)	55s
Build (nightly, bench,serde,bt,singlethreaded)	54s
stores (stores/rocksstore)	6m 5s
examples (nightly, raft-kv-memstore)	2m 22s
tests-feature-test (nightly)	2m 58s
examples (nightly, raft-kv-memstore-network-v2)	1m 8s
examples (nightly, raft-kv-memstore-opendal-snapshot-data)	1m 22s
tests-feature-test (nightly, single-term-leader)	3m 2s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 6s
examples (nightly, raft-kv-rocksdb)	6m 42s
	1h 9m 18s

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