release-22.2: roachtest: harden and extend cancel roachtest

[blathers-crl]

Backport 1/1 commits from #105569 on behalf of @yuzefovich.

/cc @cockroachdb/release

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This commit hardens cancel roachtest. In particular, this test
involves two goroutines: the runner that is executing longer running
TPCH query and the main goroutine that cancels that query. Previously,
in order to ensure that the main goroutine attempts to cancel the query
at the right moment, we slept for 250ms. Then, we would cancel all
running non-internal queries other than SHOW CLUSTER QUERIES itself.
This was problematic for a couple of reasons:

• the TPCH query might not have started yet (due some Go scheduling
  delays)
• we could actually try to cancel one of the setup queries (the runner
  does USE tpch; and SET distsql = off; before running the TPCH
  query).

In order to address the first reason, this commit adjusts the runner to
notify the main goroutine only after the setup queries are done and
introduces the polling loop to wait until the TPCH query shows up. That
polling loop will now randomly sleep for a random duration up to 1000ms
(in order to improve the test coverage of both the optimizer and the
execution engine). Note that we only check that the cancellation
occurred within 3s (used to be 5s before this commit), so we don't
sufficiently exercise the optimizer cancellation (which isn't the
primary goal of this test anyway).

The second reason is addressed by blocking the main goroutine until the
setup queries are done.

Fixes: #105528.
Fixes: #110878.

Release note: None

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Release justification: test-only change.

[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