release-23.1: sql/json: fix null's in array in inverted index support

[blathers-crl]

Backport 1/1 commits from #101059 on behalf of @cucaroach.

/cc @cockroachdb/release

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We assumed all the array elements were strings w/o checking for null,
now we use AsDString to check it.

Found internally with expanded sqlsmith testing.

Fixes: #101025
Epic: None
Release note (bug fix): Fix an internal error when optimizing JSON some exists (?|) expressions on arrays containing nulls.

---

Release justification: Fix an internal error that rejects a valid JSON query with an array containing nulls.

[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 

[yuzefovich]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rharding6373)

[rharding6373]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @cucaroach)

[mgartner]

Can you add a release note for this backport? Looks like the original was already merged, so that ship might have sailed already.

I believe this is present on v22.2 and prior? If so, then it should wait for v23.1.1, so I've added the do-not-merge label. Let me know if it's actually a regression.

[cucaroach]

I believe this is present on v22.2 and prior? If so, then it should wait for v23.1.1, so I've added the do-not-merge label. Let me know if it's actually a regression.

Yes this is present on 22.2 but not prior (22.1 didn't have any inverted index JSON optimizations).

[mgartner]

Now that the 23.1.0 branch has been cut, we can merge this. Just add a release justification first.

[github-actions]

Reminder: it has been 3 weeks please merge or close your backport!