optimizer: introduce 2 new operators for scanning sys table / CDC table

[fuyufjh]

Recommend to introduce a new physical operator CdcTableScan, because scanning from RW table, sys table or CDC table are completely different in terms of implementation.

Here the if self.predicate().always_true() actaully implies a huge difference in implementation, which should be reflected by different phyiscal operators, instead of such if-else branch.

I guess this might be introduced by sys table before, so it's acceptable for me too keep it as is now and do refactor later.

Originally posted by @fuyufjh in #12535 (comment)

[kwannoel]

+1. Arrangement backfill now requires full TableCatalog, not just the TableDesc. This creates yet another branch between RW Table (now requires full TableCatalog), Sys Table (which just has TableDesc).

I think we should refactor it before adding full TableCatalog for arrangement backfill to avoid making it even more complicated.

[kwannoel]

Additionally, they should have their own respective proto definitions as well, rather than rely on the same Chain definition.

[kwannoel]

Plan:

• Separate rw table scan and cdc scan refactor(frontend): separate cdc table scan from stream table scan #13332
• Separate rw table scan and sys scan refactor(frontend): separate sys_scan and stream_scan #13452
• Separate logical scan for cdc table. refactor: separate CdcScan from Scan in logical and core #13494
• Separate core scan for cdc table. refactor: separate CdcScan from Scan in logical and core #13494
• Separate proto: StreamTableScan, StreamCdcTableScan refactor(proto): use separate proto for cdc scan #13502

Misc:

• Unify some common functionality between different scan nodes: refactor(frontend): separate cdc table scan from stream table scan #13332 (comment)
• In Clion just look at methods underlined in yellow and unify them through some common scan library functions.
• Refactor TableDesc to SysTableDesc for sys table scan. refactor(frontend): separate sys_scan and stream_scan #13452 (comment)
• Rename Scan to TableScan to make the distinction clearer. refactor(frontend): rename generic::Scan to generic::TableScan #15837

[st1page]

Separate logical scan for cdc table.

I guess it is not needed for the logical scan, actually, I do not think there are many branches in the logical phase currently. I think just separate the physical operator is enough

after checking the current implementation, LGTM. because we do not have many common logic such as predicate push down and column pruning on the CDC table's backfill and stream scan...

[github-actions]

This issue has been open for 60 days with no activity. Could you please update the status? Feel free to continue discussion or close as not planned.

[kwannoel]

From #13146 (comment)

Unify some common functionality between different scan nodes:

It does not seem there's much in common, both between stream_table_scan and stream_cdc_scan, and also their core parts (generic::TableScan, generic::CdcScan).