Move run_with_file_number_limit.py out of pytest test suite

`run_with_file_number_limit.py` is not something pytest would collect. It should not be in the tests folder. I stumbled into a problem of the tests failing because psutil is missing but it should not have mattered.

Locate `run_with_file_number_limit.py` in the tests folder and inspect how pytest discovers files there. Move the script to an appropriate non-test location, then run the test suite without psutil to confirm unrelated tests no longer depend on it.

Written by the indexing model from the issue text.