core: layout: resize bottom row according to main layout

In the Unexpected Keyboard, the bottom row always has the width of the
main layout despite being defined with a width of 10 units. Resize the
bottom row according to the main layout to improve layouts like
arab_pc.xml and numeric.xml.

src/core/layout.rs

@@ -720,9 +720,9 @@ impl Layout {
             for key in row {
                 new_row.push(Key {
                     parts: key.parts,
-                    x1: key.x1,
+                    x1: key.x1 * layout.width / bottom_row.width,
                     y1: old_height + key.y1,
-                    x2: key.x2,
+                    x2: key.x2 * layout.width / bottom_row.width,
                     y2: old_height + key.y2,
                 });
             }