release-25.2: changefeedccl: add timeout to nemeses test inserts

[rharding6373]

Backport 1/1 commits from #146248 on behalf of @rharding6373.

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Some mutation queries take a long time to plan and execute even if they're safe. This PR adds a short timeout to each mutation, like tlp does for mutations, in order to avoid hanging.

Fixes: #146159
Epic: none

Release note: none

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Release justification: Test-only change to reduce flakiness

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

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  issues or test-only changes.
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[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 

[rharding6373]

TFTR! I guess this PR isn't recognized as test-only by the bot.