Draft: Add non-blocking way to pop JobWaiter list

What does this MR do and why?

JobWaiter#wait uses BLPOP which is a blocking call to Redis and pops a single element from the list.

This is an experiment with using LPOP which can pop off many elements at the same time to achieve the same thing.

For the Import and Integrate team's use of JobWaiter this method might be more performant.

https://gitlab.com/gitlab-org/manage/import-and-integrate/discussions/-/issues/61#note_1748410729

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