Investigation into MPIIO tuning for output files

### Are there any linked Issues or Pull Requests?

_No response_

### Brief description

The current output tuning for LFRic applications is to use the maximum number of stripes available:

```bash
lfs setstripe -c -1 $TASK_OUTPUT_DIR/results/
```

This is very likely to be non-optimal. This issue will track my investigations and experiments into tuning MPIIO to achieve more optimal write rates.

### Further details of the issue.

_No response_