Rework creating new folders in editor

[KoBeWi]

Inspired by #93372 (comment), this makes EditorFileSystem responsible for creating new folders.

I also added update_all() method to FileSystemDock. I needed it for something, but it ended up as simple helper.

[Hilderin]

I like it. The flow seems really better to me!!!

[Hilderin]

I found 2 little issues:

Issue 1

• Click create folder
• Input test/test but do not press OK
• Go create the folder test and subfolder test via File Explorer
• Got back to Godot and press OK
• The folders will be duplicate:
  

Issue 2:

• Click create folder
• Input test but do not press OK
• Go create the folder test via File Explorer
• Got back to Godot and press OK
• I expected a popup saying that the folder could not be created, but I only got an error in the output:
  

For the rest, it seems to work perfectly!! Good job, I can't wait to see the other files operations implemented that way. Don't hesitate if you need help for some implementation or some testing.

[KoBeWi]

1. fixed
2. it's a pre-existing behavior. Seems to be a bug with DirCreateDialog, which validates path before attempting to create the folder.

[Hilderin]

Great!!
Tested and works perfectly, as expected!

[akien-mga]

Thanks!