feat: Defines more structs and methods for a partitioned merge tree #13519

Job	Run time
Rustfmt	28s
Build GreptimeDB binaries (ubuntu-20.04)	4m 12s
Check (windows-latest)	7m 46s
Check (ubuntu-20.04)	1m 39s
Toml Check	22s
Spell Check with Typos	15s
Clippy	1m 56s
coverage	10m 58s
Compatibility Test	27s
Sqlness Test (ubuntu-20.04)	1m 55s
Sqlness Test with Kafka Wal (ubuntu-20.04)	2m 17s
	32m 15s

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