Manage multiple simultaneous and background PM/Sim Runs

Currently, when starting one PM or Sim run, users need to stay on the respective page to wait for termination and cannot start other runs or use different pages.

It might be sensible to
- Enable users to have multiple runs at the same time, e.g., to compare different scenario variants or to parallelize PM and simulation
- [x] Allow users to leave the PM/Sim page during a run and come back later, e.g., to prepare the next run.

Proposals:
- Create one box for each run, that shows its status and, if applicable, outputs. It also allows to convert from this specific run (to not mix files), and to cleanup the files from that specific run.

No files or tests are named. Start by tracing the PM and Sim page run flows, including how a run reports status and produces outputs. Done means users can leave those pages, start multiple PM or simulation runs, return to view each status and outputs, convert a selected run without mixing files, and clean up that run's files.

Written by the indexing model from the issue text.