release-22.1: sql: audit all processors to make their closure bullet-proof

[yuzefovich]

Backport 1/1 commits from #91969.

/cc @cockroachdb/release

---

This commit replaces all usages of ProcessorBaseNoHelper.Ctx field
with a call to the newly-introduced Ctx() method which returns
a background context if the processor hasn't been started. This change
makes it so that all processors now respect the contract of
colexecop.Closer interface which says that Close must be safe to
call even if Init hasn't been performed (in the context of processors
this means that Columnarizer.Init wasn't called meaning that
Processor.Start wasn't either).

Initially, I attempted to fix this in #91446 by putting the protection
into the columnarizer, but that led to broken assumptions since we
wouldn't close all closers that we expected to (in particular, the
materializer that is the input to the wrapped row-by-row processor
wouldn't be closed). This commit takes a different approach and should
fix the issue for good without introducing any flakiness.

As a result, this commit fixes a rarely hit issue when the aggregator
and the zigzag joiner attempt to log when they are closed if they
haven't been started (that we see occasionally from sentry). The issue
is quite rare though, so no release note seems appropriate.

Fixes: #84902.
Fixes: #91845.

Release note: None

Release justification: low-risk bug fix.

[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 

[rytaft]

(perhaps this should bake on master for a bit, though?)

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @cucaroach)

[yuzefovich]

Yes, I want to let it bake on master for a week or so..

[yuzefovich]

Looks like there hasn't been any fallout, merging.