Fix: Mis-sized widgets due to missing widget fill. (#14370)

In most places where we calculate and set widget resize step we neglect
to set widget fill step to match. Initial widget sizing uses fill step
instead of resize step, which means the initial size may not be a
multiple of the resize step as intended. In particular this will cause
WWT_MATRIX to be misrendered.

Whether or not this matters depends on the widget type being resized and
the window layout, however for consistency always set fill step to the
same as resize step when calculating.

src/graph_gui.cpp

@@ -1163,7 +1163,7 @@ struct BaseCargoGraphWindow : BaseGraphWindow {
 		this->line_height = size.height;
 		size.height = this->line_height * 11; /* Default number of cargo types in most climates. */
 		resize.width = 0;
-		resize.height = this->line_height;
+		fill.height = resize.height = this->line_height;
 	}
 
 	void DrawWidget(const Rect &r, WidgetID widget) const override