change(ci): Split experimental feature tests into their own step

[teor2345]

Motivation

This PR will make ticket #8037 easier to do, by making it easier to find and read the log output.

PR Author Checklist

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• Will the PR name make sense to users?
• Does the PR have a priority label?
• Have you added or updated tests?
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Solution

• Split the experimental feature test output into its own step, so it's easier to find
• Reduce log output during tests by only logging a checkpoint warning once (rather than for each checkpoint)

Testing

The existing tests cover these changes.

Review

This is a low priority cleanup.

Reviewer Checklist

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• Does the PR scope match the ticket?
• Are there enough tests to make sure it works? Do the tests cover the PR motivation?
• Are all the PR blockers dealt with?
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Follow Up Work

Actually fix and enable #8037

[arya2]

Looks good!