opt/execbuilder: fix EXPORT when input expression has hidden columns

[mgartner]

opt/execbuilder: fix EXPORT when input expression has hidden columns

Fixes #115290

Release note (bug fix): A bug has been fixed that caused internal errors
when executing EXPORT statement.

opt/execbuilder: remove getNodeColumnOrdinalSet

This simple function was only used in one place, so it has been inlined
and removed.

Release note: None

[cockroach-teamcity]

This change is 

[rytaft]

nice!

Reviewed 2 of 2 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @DrewKimball and @yuzefovich)

[rytaft]

Probably worth backporting this too, right?

[DrewKimball]

Reviewed 2 of 2 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! 2 of 0 LGTMs obtained (waiting on @yuzefovich)

[mgartner]

Probably worth backporting this too, right?

Yes - added the labels.

[mgartner]

TFTRs!

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from 592272c to blathers/backport-release-23.1-119538: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.1.x failed. See errors above.

---

error creating merge commit from 592272c to blathers/backport-release-23.2-119538: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.2.x failed. See errors above.

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