Optimize meta memory usage

[xxchan]

Background: https://www.notion.so/risingwave-labs/Jindo-Meta-OOM-752dedb74fac4e668fe4863c62318fbb?pvs=4

Meta consumed a lot of memory. And can consume a lot higher memory during some processes than the stable usage and OOM.

A known memory allocation involves duplicating all actors and distributing them to CNs for the recovery process.
by @yezizp2012

[xxchan]

Can SQL backend reduce memory usage? 🤔

[yezizp2012]

Can SQL backend reduce memory usage? 🤔

Yes, meta will not maintain a cache of table fragments, this part of the memory that is always resident will be saved. For recovery, I had a offline discussion with @shanicky , we gonna fully deprecate table fragments and reduce the memory usage and RPC request body in the future.