`end_run(immediate=True)` - use mechanism compatible with client/server split

[Tom-Willemsen]

The current mechanism of writing to a local file breaks client/server split and wouln't work if the python session is not on the same computer that is running the ISISICP.

genie/src/genie_python/genie_dae.py

Line 488 in 639ab86

self._write_to_end_now_file("1")

[rerpha]

also set_simulation_mode(): https://github.com/ISISComputingGroup/genie/blob/main/src/genie_python/genie_dae.py#L2110 which relies on https://github.com/ISISComputingGroup/genie/blob/main/src/genie_python/genie_dae.py#L134

[rerpha]

and most things in https://github.com/search?q=repo%3AISISComputingGroup%2Fgenie+C%3A&type=code&p=1