Workflow: Single File From Series Renamed & Read

In https://github.com/ECP-WarpX/WarpX/pull/1937, we have a new workflow that takes a single file from a series using a `fileBased` iteration encoding, renames it to e.g. `input.h5` and reads a single iteration back.

We have not yet considered such use cases, because they would break the defined `iterationEncoding` in the file. We should thus add a CI test to make sure such a workflow works on the long-term.