Clear bob files from screen directory

[shihab-dls]

Currently, fastCS services PVCs that contains the generated bob files keeps old files. It would be nice to generate new bob files in a temp directory, then delete bob files in the PVC once the new bob files have successfully been generated, then move the new bob files over, upon IOC start-up. This would require a change inserted into:

    def create_gui(self, options: EpicsGUIOptions | None = None) -> None:
        if options is None:
            options = EpicsGUIOptions()

        if options.file_format is EpicsGUIFormat.edl:
            logger.warning("FastCS may not support all widgets in .edl screens")

        assert options.output_path.suffix == options.file_format.value
        options.output_path.parent.mkdir(parents=True, exist_ok=True)

        components = self.extract_api_components(self._controller_api)
        device = Device(label=options.title, children=components)

        formatter = DLSFormatter()
        formatter.format(device, options.output_path.resolve())

Acceptance Criteria

• Screens directory is appropriately cleared at start-up

[GDYendell]

I think this is probably the right thing to do, but I am just wondering if there is some context where we wouldn't want this. Could we ever be in a situation where pressing a button on a UI fails to load the screen because it has been deleted? I suppose it would likely mean that all of the PVs on that screen are disconnected, but that might be better than the screen not opening at all.

@coretl, @gilesknap?

[coretl]

I can't think of a reason we would want the keep an old screen with disconnected PVs on it, probably less confusing to get a 404 than an out of date screen