refactor: split regular and existence join in hash join #24791

Is your feature request related to a problem or challenge?

Regular joins (inner/left/right/full) and existence joins (anti/semi/mark) are different relational operations; separating them can potentially make them simpler and easier to maintain.

The following issue describes the why. I believe it's a different problem, but with exactly the same core philosophy, and it provides a more detailed writeup.

• [EPIC] Split Aggregation Logic into Dedicated Streams #22710

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