Change: Replace `loosen-follower-log-revert` feature flag with `Config::allow_log_reversion` #4188

Job	Run time
cluster-benchmark (cluster_benchmark)	43s
openraft-test (stable, 0)	45s
openraft-test (nightly, 30)	45s
openraft-test-bench (nightly)	50s
openraft-test (nightly, 0, single-term-leader)	46s
stores (stores/memstore)	45s
examples (stable, memstore)	43s
stores (stores/rocksstore)	6m 6s
examples (stable, raft-kv-memstore)	1m 36s
examples (stable, raft-kv-memstore-network-v2)	46s
examples (stable, raft-kv-memstore-opendal-snapshot-data)	1m 4s
lint	58s
stores (stores/sledstore)	54s
examples (stable, raft-kv-memstore-singlethreaded)	49s
examples (stable, raft-kv-rocksdb)	6m 35s
openraft-feature-test (nightly)	48s
examples (nightly, memstore)	56s
rt-monoio	42s
openraft-feature-test (nightly, serde)	47s
examples (nightly, raft-kv-memstore)	1m 19s
examples (nightly, raft-kv-memstore-network-v2)	48s
openraft-feature-test (nightly, single-term-leader)	46s
examples (nightly, raft-kv-memstore-opendal-snapshot-data)	1m 1s
Build (nightly, bench,serde,bt,singlethreaded)	53s
examples (nightly, raft-kv-memstore-singlethreaded)	48s
examples (nightly, raft-kv-rocksdb)	6m 58s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	47s
tests-feature-test (nightly)	49s
tests-feature-test (nightly, single-term-leader)	49s
	42m 16s

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