Meta+Userland: Run the GML formatter on CI and pre-commit

Now that the GML formatter is both perserving comments and also mostly
agrees to the existing GML style, it can be used to auto-format all the
GML files in the system. This commit does not only contain the scripts
for running the formatting on CI and the pre-commit hook, but also
initially formats all the existing GML files so that the hook is
successfull.

Userland/Libraries/LibGUI/FilePickerDialog.gml

@@ -1,6 +1,5 @@
 @GUI::Widget {
     fill_with_background_color: true
-
     layout: @GUI::HorizontalBoxLayout {
         margins: [4]
         spacing: 3