LibGfx: Fix some more antialiased line off-by-ones

Turns out most things expect lines to include the endpoint,
e.g. 0,0 -> 3,0 is a 4px long line. But the fill_path() implementation
seems to expect the line to be the distance between the two points
(so the above example is a 3px line instead).

This now adds an option to pick between PointToPoint line length or
Distance line length and uses the latter for fill_path().

Userland/Libraries/LibGfx/FillPathImplementation.h

@@ -47,8 +47,8 @@ void fill_path(Painter& painter, Path const& path, Color color, Gfx::Painter::Wi
     using GridCoordinateType = Conditional<fill_path_mode == FillPathMode::PlaceOnIntGrid, int, float>;
     using PointType = Point<GridCoordinateType>;
     auto draw_line = [&](auto... args) {
-        if constexpr (requires { painter.draw_line_for_path(args...); })
-            painter.draw_line_for_path(args...);
+        if constexpr (requires { painter.draw_line_for_fill_path(args...); })
+            painter.draw_line_for_fill_path(args...);
         else
             painter.draw_line(args...);
     };