Change: refine the `RaftEntry` trait #4321

Job	Run time
test-crate-tests (stable, 0)	3m 15s
openraft-test-bench (nightly)	1m 0s
test-crate-tests (nightly, 30)	3m 12s
test-crate-openraft (stable)	1m 1s
Build (nightly, bench,serde,bt,singlethreaded)	56s
test-crate-tests (nightly, 0, single-term-leader)	3m 4s
test-crate-openraft (nightly)	55s
cluster-benchmark (cluster_benchmark)	45s
examples (stable, memstore)	42s
lint	4m 7s
rt-monoio	46s
examples (stable, rocksstore)	5m 32s
examples (stable, raft-kv-memstore)	3m 29s
openraft-feature-test (nightly)	51s
stores (stores/memstore)	57s
examples (stable, raft-kv-memstore-grpc)	1m 51s
tests-feature-test (nightly)	2m 58s
openraft-feature-test (nightly, serde)	57s
examples (stable, raft-kv-memstore-network-v2)	1m 20s
tests-feature-test (nightly, single-term-leader)	3m 5s
openraft-feature-test (nightly, serde,singlethreaded)	52s
examples (stable, raft-kv-memstore-opendal-snapshot-data)	1m 10s
examples (stable, raft-kv-memstore-singlethreaded)	1m 12s
examples (stable, raft-kv-rocksdb)	6m 9s
examples (nightly, memstore)	58s
examples (nightly, rocksstore)	5m 45s
examples (nightly, raft-kv-memstore)	2m 27s
examples (nightly, raft-kv-memstore-grpc)	1m 48s
examples (nightly, raft-kv-memstore-network-v2)	1m 13s
examples (nightly, raft-kv-memstore-opendal-snapshot-data)	1m 28s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 11s
examples (nightly, raft-kv-rocksdb)	6m 9s
	1h 11m 5s

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