refactor: use `inserter` instead of `grpc_handler` in pipeline operator #33

Job	Run time
Check (windows-2022)	10m 6s
Check License Header	1m 13s
Check (ubuntu-20.04)	3m 55s
Build GreptimeDB binaries (ubuntu-20.04)	8m 14s
Build GreptimeDB binary (profile-CI) (ubuntu-20.04)	7m 1s
Check typos and docs	5s
Rustfmt	1m 2s
Toml Check	51s
Clippy	4m 20s
coverage	1s
Fuzz Test (Distributed, Disk) (fuzz_create_table)	7m 5s
Fuzz Test (Distributed, Disk) (fuzz_alter_table)	6m 59s
Fuzz Test (Distributed, Disk) (fuzz_create_database)	7m 57s
Fuzz Test (Distributed, Disk) (fuzz_create_logical_table)	7m 58s
Fuzz Test (Distributed, Disk) (fuzz_alter_logical_table)	7m 49s
Fuzz Test (Distributed, Disk) (fuzz_insert)	8m 28s
Fuzz Test (Distributed, Disk) (fuzz_insert_logical_table)	9m 17s
Unstable Fuzz Test (unstable_fuzz_create_table_standalone)	12m 47s
Fuzz Test (fuzz_create_table)	5m 9s
Fuzz Test (fuzz_alter_table)	5m 40s
Sqlness Test with Kafka Wal (ubuntu-20.04)	3m 9s
Sqlness Test (ubuntu-20.04)	2m 25s
Fuzz Test (fuzz_create_database)	5m 58s
Fuzz Test (fuzz_create_logical_table)	5m 22s
Fuzz Test (fuzz_alter_logical_table)	6m 22s
Fuzz Test (fuzz_insert)	5m 1s
Fuzz Test (fuzz_insert_logical_table)	5m 27s
	2h 29m 41s

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