release-24.3: ci-stress: skip stressing if there are no tests

[rickystewart]

Backport 1/1 commits from #160014 on behalf of @rickystewart.

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Release note: none
Epic: DEVINF-1582

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Release justification: Non-production code changes

[blathers-crl]

Thanks for opening a backport.

Before merging, please confirm that it falls into one of the following categories (select one):

• Non-production code changes. Includes test-only changes, build system changes, etc.
• Fixes for serious issues. Defined in the policy as correctness, stability, or security issues, data corruption/loss, significant performance regressions, breaking working and widely used functionality, or an inability to detect and debug production issues.
• Other approved changes. These changes must be gated behind a disabled-by-default feature flag unless there is a strong justification not to.

Add a brief release justification to the PR description explaining your selection.

Also, confirm that the change does not break backward compatibility and complies with all aspects of the backport policy.

All backports must be reviewed by the TL and EM for the owning area.

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[blathers-crl]

✅ PR #160019 is compliant with backport policy

Confidence: high
Backward compatible: true
Explanation: The PR addresses changes in the pkg/cmd/ci-stress/main.go, which is a development tool as listed under the pattern pkg/cmd/roachtest/. Such files are included in the exception list for non-production and test-only changes. Therefore, they do not need to meet the critical bug justification or feature flag requirements. Moreover, the PR body mentions a 'Release justification: Non-production code changes', which exempts it from regular backport policy requirements. Although the pattern mentioned in the policy is not exactly pkg/cmd/ci-stress/, it falls under the broader scope of development tools similar to pkg/cmd/roachtest/, justifying the exemption.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}