Add already existing localisation support from CommonStrings (#37401)

decided to do this mostly because of the non-localised `BackButton` that
was bothering my eyes

changes can be reviewed commit by commit

osu.Game/Graphics/UserInterface/TwoLayerButton.cs

@@ -10,6 +10,7 @@ using osu.Framework.Graphics.Effects;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Input.Events;
+using osu.Framework.Localisation;
 using osu.Game.Beatmaps.ControlPoints;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.Sprites;
@@ -161,7 +162,7 @@ namespace osu.Game.Graphics.UserInterface
             set => bouncingIcon.Icon = value;
         }
 
-        public string Text
+        public LocalisableString Text
         {
             set => text.Text = value;
         }