refactor: merge standalone and metasrv table metadata allocators (#3035) #12118

Job	Run time
Check (windows-latest-8-cores)	1m 47s
Check (ubuntu-20.04)	1m 13s
Spell Check with Typos	19s
Sqlness Test (ubuntu-20.04-8-cores)	3m 24s
Toml Check	31s
Rustfmt	23s
Sqlness Test with Kafka Wal (ubuntu-20.04-8-cores)	3m 55s
Clippy	1m 40s
coverage	9m 46s
	22m 58s

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