release-25.1: roachtest: collect qps metrics over longer window in gracefuldrain test

[blathers-crl]

Backport 1/1 commits from #139273 on behalf of @arulajmani.

/cc @cockroachdb/release

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The gracefuldrain test was modernized in cf30717. Prior to that commit, QPS metrics were collected over a 10s interval, whereas the modernization refactor changed this to 1 second intervals. Looking at a few recent test failures, I see QPS metrics above the failure threshold, which makes me think suspect that this 1s interval is causing the sorts of inaccuracies MeasureQPS warns against. Also See #133020 (comment).

One thing that doesn't line up is the timeline of this tests failure and cf30717. Still, this patch changes the metric's interval back to 10s.

References #133020

Release note: None

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Release justification: test-only change.

[blathers-crl]

Thanks for opening a backport.

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[cockroach-teamcity]

This change is