release-21.2: sql/delegate: pick up new 21.2 columns in SHOW JOBS

[blathers-crl]

Backport 1/1 commits from #70766 on behalf of @ajwerner.

/cc @cockroachdb/release

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New columns were added to crdb_internal.jobs to expose retry and
exponential backoff state. This commit exposes them in SHOW JOBS.

No need for a version gate because the virtual table is local and will
just populate the columns with NULL in the mixed version state.

Fixes #70765.

Release note (sql change): SHOW JOBS will now include the newly added
columns from crdb_internal.jobs (last_run, next_run, num_runs,
and execution_errors). The columns capture state related to retries,
failures, and exponential backoff.

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Release justification:

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues.
• 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]

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

[ajwerner]

This got sign-off in the meeting.