release-21.2: opt: support BYTES for histogram range calculations

[mgartner]

Backport 1/2 commits from #68740.

/cc @cockroachdb/release

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Fixes #68346

Release note (performance improvement): The accuracy of histogram
calculations for BYTES types has been improved. As a result, the
optimizer should generate more efficient query plans in some cases.

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Release justification: This fix can greatly improve query plans that filter
on inverted index columns.

[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 

[mgartner]

A customer was seeing suboptimal plans in 21.2.4, and it is fixed by this commit. It seems safe enough to backport, but let me know if you disagree.

[rytaft]

Reviewed 6 of 6 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @michae2)