release-23.1: importer: disallow subqueries in function arguments for pg_dump

[blathers-crl]

Backport 1/1 commits from #118569 on behalf of @DrewKimball.

/cc @cockroachdb/release

---

Some functions can modify the db schema, and so can be included in a pg_dump file. The pg_dump importer logic type-checks such functions, which can lead to a nil-pointer panic in cases like the following: SELECT addgeometrycolumn('t', 'foo', 4326, (SELECT 'POINT'), 2) This is because subqueries cannot be type-checked outside the optbuilder, which sets the type annotation for the subquery.

This patch explicitly disallows subqueries in the type-checking that happens for processing a pg_dump file. This will ensure that users get an expected subqueries are not allowed in pg_dump function arguments error, instead of the panic.

Fixes #117724

Release note (bug fix): Fixed a rare panic that could happen during a pg_dump import that contains a function like SELECT addgeometrycolumn(...). Now, attempting to import a pg_dump with a function that has a subquery in one of its arguments results in an expected error.

---

Release justification: fix panic in pg_dump import

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
• Backports should not change on-disk formats or node communication protocols.
• Backports should not add new functionality (except as defined
  here).
• Backports must not add, edit, or otherwise modify cluster versions; or add version gates.
• All backports must be reviewed by the owning areas TL and one additional
  TL. For more information as to how that review should be conducted, please consult the backport
  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• 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. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added).
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.
• Your backport must be accompanied by a post to the appropriate Slack
  channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is