Add option to enqueue registry migration twice

What does this MR do and why?

We are working on migrating all container repositories to the new container registry. The process is driven by rails. The EnqueuerWorker is responsible for finding the next qualified container repository to import and starting the import process. We control the number of EnqueuerWorker jobs by checking the capacity, meaning, we allow up to a certain number of container repositories to be importing at the same time. If the capacity is not yet met, we enqueue one more job, if it is met, we don't. Similarly, when an import finishes, we enqueue one more job.

Unfortunately, while we currently are allowing for up to 25 imports at one time (see #361368 (closed) for metric details), we aren't enqueing fast enough to reach that limit, which means we are going slower than we could. We would like to increase to reach full capacity since this migration is on a strict timeline.

In this MR, instead of re-enqueueing once for each of the conditions described above, we enqueue twice. We put the 2nd enqueue call behind a feature flag so we have full control over how many times we are starting these jobs.

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How to set up and validate locally

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Related: #361368 (closed)