Split Actor.Bounds into RenderBounds and SelectableBounds

Additionally, internally renamed VisualBounds to SelectionOverlayBounds to avoid confusion with RenderBounds.

This step was necessary to prevent actors with selectable area smaller than their graphics to be removed too early from ScreenMap even though part of the graphics should still be visible.
RA cruisers were a prime example, but to a lesser extent several other actors were affected as well.

This separation also serves as preparation to determine the final RenderBounds from multiple source bounds later, to fix the remaining ScreenMap issues (building 'bibs', aircraft shadows).

OpenRA.Mods.Common/Traits/Render/WithTextDecoration.cs

@@ -95,7 +95,7 @@ namespace OpenRA.Mods.Common.Traits.Render
 			if (!ShouldRender(self) || self.World.FogObscures(self))
 				return Enumerable.Empty<IRenderable>();
 
-			var bounds = self.VisualBounds;
+			var bounds = self.SelectionOverlayBounds;
 			var halfSize = font.Measure(Info.Text) / 2;
 
 			var boundsOffset = new int2(bounds.Left + bounds.Right, bounds.Top + bounds.Bottom) / 2;