feat: impl merge reader for DataParts (#3361) #13589

Job	Run time
Check (windows-latest)	3m 48s
Spell Check with Typos	22s
Check (ubuntu-20.04)	1m 22s
Toml Check	15s
Build GreptimeDB binaries (ubuntu-20.04)	3m 59s
Clippy	1m 56s
coverage	10m 30s
Rustfmt	25s
Compatibility Test	40s
Sqlness Test (ubuntu-20.04)	1m 41s
Sqlness Test with Kafka Wal (ubuntu-20.04)	3m 48s
	28m 46s

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