Add a margin to EditorSpinSlider to visually line up the edited number
Add a margin to EditorSpinSlider to visually line up the edited number

This means clicking on an EditorSpinSlider to edit its value will
no longer cause the number to be visually offset while it's
being edited.

(cherry picked from commit cc615fee5f88d543fb5877ddd0207b832772f7fe)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot