Refactor: delete async-trait, fix typo, use tokio to replace async_std #22

Job	Run time
external-stores (stores/rocksstore-v2)	5m 52s
examples (stable, raft-kv-memstore)	2m 19s
cluster-benchmark (cluster_benchmark)	46s
examples (stable, raft-kv-memstore-singlethreaded)	57s
lint	6m 22s
examples (stable, raft-kv-rocksdb)	6m 27s
openraft-feature-test (nightly)	47s
openraft-test (stable, 0)	2m 54s
examples (nightly, raft-kv-memstore)	2m 15s
openraft-feature-test (nightly, serde)	53s
openraft-test (nightly, 30)	3m 13s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 19s
openraft-feature-test (nightly, single-term-leader)	46s
openraft-test-bench (nightly)	52s
openraft-test (nightly, 0, single-term-leader)	2m 58s
examples (nightly, raft-kv-rocksdb)	6m 25s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	50s
Build (nightly, bench,serde,bt,singlethreaded)	51s
stores (memstore)	42s
tests-feature-test (nightly)	2m 43s
stores (rocksstore)	5m 58s
tests-feature-test (nightly, single-term-leader)	2m 44s
stores (rocksstore-compat07)	6m 17s
tests-feature-test (nightly, loosen-follower-log-revert)	2m 51s
stores (sledstore)	52s
	1h 8m 53s

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