Use until_executed deduplication for CoverageReportWorker

What does this MR do and why?

Use until_executed deduplication for CoverageReportWorker

This worker can be executed concurrently and its transactions don't handle the uniquness error from trying to insert multiple artifacts of the same type. Allowing only one worker to execute at a time should fix that error.

Screenshots or screen recordings

This worker has the biggest error rate in our group, over 25k errors in the last month:

source

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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