UI: Preference to Always Show Number Arrows

Numerical inputs have little arrows on the left and right to allow
quick increment/decrement of the value. But these are only shown on
hover, which does not help if using a device that does not have a hover
state (some pens, most touch). This PR adds a user preference to show
them always.

Pull Request: https://projects.blender.org/blender/blender/pulls/145374

scripts/startup/bl_ui/space_userpref.py

@@ -293,8 +293,13 @@ class USERPREF_PT_interface_editors(InterfacePanel, CenterAlignMixIn, Panel):
 
         col = layout.column()
         col.prop(system, "use_region_overlap")
+
+        col = layout.column(heading="Show", align=True)
         col.prop(view, "show_area_handle")
+        col.prop(view, "show_number_arrows", text="Numeric Input Arrows")
         col.prop(view, "show_navigate_ui")
+
+        col = layout.column()
         col.prop(view, "border_width")
         col.prop(view, "color_picker_type")
         col.row().prop(view, "header_align")