release-22.1: sql: fix assignment casts of arrays

[mgartner]

Backport 1/6 commits from #102491.

/cc @cockroachdb/release

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sql: fix assignment casts of arrays

This commit fixes a bug that caused incorrect results for assignment
casts of array types. Previously, the array's elements were casted as an
explicit cast, not an assignment cast. This allowed values to be
inserted into an array column that did not conform to the type.

Fixes #102412

Release note (bug fix): A bug has been fixed that allowed values to be
inserted into an ARRAY-type column that did not conform to the
inner-type of the array. For example, it was possible to insert
ARRAY['foo'] into a column of type CHAR(1)[]. This could cause
incorrect results when querying the table. The insert now errors, which
is expected. This bug was present since v21.1.

---

Release justification: Fix for a correctness bug related to assignment
casts.

[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 

[michae2]

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