test(engineio): mock http/ws connections and improve integration tests #1142

Job	Run time
test	1m 46s
msrv	23s
feature_set	4m 36s
examples	29s
format	11s
rust-clippy-analyze	49s
udeps	49s
engine_io (v3)	31s
engine_io (v4)	30s
socket_io (v4)	1m 0s
socket_io (v5)	45s
socket_io (v5-msgpack)	42s
adapter (v4, fred-e2e)	1m 12s
adapter (v4, redis-e2e)	1m 12s
adapter (v4, redis-cluster-e2e)	1m 12s
adapter (v4, fred-cluster-e2e)	1m 16s
adapter (v4-msgpack, fred-e2e)	1m 44s
adapter (v4-msgpack, redis-e2e)	1m 13s
adapter (v4-msgpack, redis-cluster-e2e)	1m 13s
adapter (v4-msgpack, fred-cluster-e2e)	1m 13s
adapter (v5, fred-e2e)	1m 20s
adapter (v5, redis-e2e)	1m 24s
adapter (v5, redis-cluster-e2e)	1m 11s
adapter (v5, fred-cluster-e2e)	1m 14s
adapter (v5-msgpack, fred-e2e)	1m 39s
adapter (v5-msgpack, redis-e2e)	1m 19s
adapter (v5-msgpack, redis-cluster-e2e)	1m 52s
adapter (v5-msgpack, fred-cluster-e2e)	1m 12s
all_passed	1s
	33m 58s

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