GUI: Script Generator doesn't show 'Reloading' screen when used from IBEX GUI

### Description
As a Script Generator user I would like it to be consistent when ran both as standalone and from IBEX GUI. Currently if Script Generator is run from IBEX GUI and following steps are reproduced, the Script Gen will come back with correct state but will not show 'Reloading' screen while at it.

### Steps to reproduce:
- Open script generator in IBEX GUI,
- Delete the Python process that the Script Generator is using
- Might need to play around a little to trigger reloading
- Should reload and keep it's state from before deleting the process but doesn't show 'Reloading' screen

This is connected to the ticket: [#6690](https://github.com/ISISComputingGroup/IBEX/issues/6690)
You can see how 'Reloading' screen should look like by following steps in that ticket, but until that ticket is complete
it actually gets stuck on said screen.

### Acceptance criteria:
- When run Script Generator from IBEX GUI and reproducing the steps, 'Reloading' screen should show up
and Script Generator should be restored after couple of seconds with previous state (all actions are the same, same script definition loaded etc.)
- There is a Squish test for this
- This behaviour is consistent when ran from IBEX GUI as well as standalone