Separate WrappedLines from ShapedLines

ShapedLines are never wrapped, whereas WrappedLines are optionally wrapped if
they are associated with a wrap width. I tried to combine everything because
wrapping is inherently optional for the Text element, but we have a bunch of
APIs that don't make sense on a line that may wrap, so we need a distinct type
for that case.

crates/gpui2/src/element.rs

@@ -13,7 +13,7 @@ pub trait Element<V: 'static> {
     fn layout(
         &mut self,
         view_state: &mut V,
-        previous_element_state: Option<Self::ElementState>,
+        element_state: Option<Self::ElementState>,
         cx: &mut ViewContext<V>,
     ) -> (LayoutId, Self::ElementState);