release-22.1: opt: fix bug with incorrect results produced by paired left lookup join

[rytaft]

Backport 1/1 commits from #82054.

/cc @cockroachdb/release

Release justification: fixes a critical correctness issue

---

Prior to this patch, it was possible for a paired join to produce incorrect
results for a left lookup join. In particular, some output rows had
non-NULL values for right-side columns when the right-side columns should
have been NULL.

This commit fixes the issue by updating the optimizer to ensure that
only columns from the second join in the paired join (the index join)
are projected, not columns from the first (the lookup join).

Fixes #81968

Release note (bug fix): Fixed an issue where a left lookup join could
have incorrect results. In particular, some output rows could have non-NULL
values for right-side columns when the right-side columns should
have been NULL. This issue only exists in 22.1.0 and prior development
releases of 22.1.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[msirek]

Reviewed 6 of 6 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @yuzefovich)