Rewrite CommonSubexprEliminate to avoid copies using TreeNode

[alamb]

WIP -- still has many more copies to remove

Which issue does this PR close?

Part of #9637

related to #9873

Rationale for this change

Let's make planning faster by not copying so much in the optimizer using the new TreeNode API.

What changes are included in this PR?

1. See PR subject

Note this pass still leaves a lot to be desired in terms of copying Exprs / making strings but it is much better now. Fixing up the additional copies is tracked with #9873

Are these changes tested?

Functional: existing tests
Performance: TBD

Are there any user-facing changes?

[peter-toth]

@alamb, can I take this PR and rebase it on the latest main? It would be better to refactor CSE rule to use rewrite() before I can finish my #10473.

[alamb]

@alamb, can I take this PR and rebase it on the latest main? It would be better to refactor CSE rule to use rewrite() before I can finish my #10473.

Sure -- that would be great @peter-toth -- I actually had a secret plan to work on the CSE rewrite tomorrow (I swear!) as I will be traveling and on a plane ✈️ -- but if you would like to take it that would be great (I have several other things that I would love to work on as well)

Just let me know what you want to do

[peter-toth]

Sure, please work on it if you have some time during the weekend as I can't do it earlier than next week.
Let me know how it goes and I can take this next week if you don't have time.

[alamb]

Sure, please work on it if you have some time during the weekend as I can't do it earlier than next week. Let me know how it goes and I can take this next week if you don't have time.

Will do -- thank you

[alamb]

Superceded by #10835, will continue work there