feat: Implement KeyDictBuilder for the merge tree memtable (#3334) #13464

Job	Run time
Spell Check with Typos	21s
Check (windows-latest)	5m 25s
Toml Check	34s
Check (ubuntu-20.04)	2m 2s
Build GreptimeDB binaries (ubuntu-20.04)	5m 19s
Clippy	2m 11s
coverage	11m 30s
Rustfmt	37s
Sqlness Test (ubuntu-20.04)	1m 43s
Compatibility Test	43s
Sqlness Test with Kafka Wal (ubuntu-20.04)	2m 23s
	32m 48s

Provide feedback