Add pre-validation for various slurm option as client hangs if launch fails

```
>>> import ansys.fluent.core as pyfluent
>>> slurm = pyfluent.launch_fluent(scheduler_options={"scheduler": "slurm", "scheduler_headnode": "nonsense"}, ui_mode="no_gui_or_graphics")
ssh: Could not resolve hostname nonsense: Name or service not known
>>> exit() # hangs
```

This issue was originally reported in PyConsole (Fluent bug 1115063).

Start from pyfluent.launch_fluent and its scheduler_options handling, using the reproduced Slurm launch with scheduler_headnode set to "nonsense" as the failure case. Trace how the failed SSH launch is handled; done means invalid Slurm options are rejected before launch and exiting the client no longer hangs.

Written by the indexing model from the issue text.