release-22.2: sql/schemachanger: address bugs with column families

[fqazi]

Backport 1/3 commits from #99953.

/cc @cockroachdb/release

---

sql: avoid writing to column families that do not exist in the primary index

Previously, if a new column family was added during an add
column and an update/insert occurred concurrently, we could
end up writing to this new column family in any primary index.
This was inadequate because if the primary index did not store
the column, then runtime will have trouble reading data from this
table, since after a rollback the added column / column family
will get cleaned up from the table descriptor. To address this,
this patch avoids writing any columns not stored within an index
descriptor.

Fixes: #99950

Release note (bug fix): Concurrent DML while adding
a new column with a new column family can lead to
corruption in the existing primary index. If a rollback
occurs the table may no longer be accessible.

Release justification: low risk and avoids bad KV's inside primary indexes during rollback

[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 

[fqazi]

@chengxiong-ruan TFTR!