Editor: Use HFlowContainer to display file dialog options

[HolonProduction]

Followup to #80561 which improves the UI a bit:

Before

After

Since we are not using a grid container anymore I also switched to using the checkbox label instead of an additional one. This improves usability a bit since the text is now also a click target.

[KoBeWi]

Related to #95304 and #95140
I think the options were vertical to be more consistent with native dialogs. CC @bruvzg

[bruvzg]

It depends on the platform, on Linux (at least GTK) it's also horizontal. So it should be file, as long as both checkbox and dropdown options look OK.

[HolonProduction]

Dropdowns still work and also the label can't be on another line than the dropdown. Only point that might be somewhat controversial is that dropdowns show the label and then the dropdown while checkboxes show the checkbox and then the label.

I looked at Gnome for inspiration regarding this and they do it exactly the same, so it should be fine, especially since there are no dropdowns in the codebase at the moment (plugins might use them though).

[KoBeWi]

This can resolve #95079 if the same change is done for FileDialog.

EDIT:
Well that issue is about editor-only, just the same bug applies to FileDialog too.

[bruvzg]

Only point that might be somewhat controversial is that dropdowns show the label and then the dropdown while checkboxes show the checkbox and then the label.

Same on Windows. It's not the case only on macOS, but on macOS we can change this as we want: