release-23.2.6-rc: sql: drop user/role did not detect usage by types

[fqazi]

Backport 1/1 commits from #124611.

/cc @cockroachdb/release

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Previously, it was possible to drop a user / role in use by a type because the detection logic only checked ownership. To address this, this patch will check if the user exists within any types before allowing the drop to go through.

Note: An automated repair during upgrade exists to fix descriptors with this issue, since they can break SHOW GRANTS. The same repair query can also be invoked manually.

Fixes: #124441

Release note (bug fix): Drop role/user could leave references behind inside types, which could prevent SHOW GRANTS from working

Release justification: low risk fix that blocks an operation that could lead to description corruption (breaking SHOW GRANTS)

[blathers-crl[bot]]

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 

[fqazi]

@rafiss @dhartunian TFTR!