message: Use tesselator+path builder in rounded_rectangle
  `rounded_rectangle` was moved from `basic_shapes` to `PathBuilder`, so
  we must now build a path with `add_rounded_rectangle`, then tesselate
  it.
diff: @@ -339,24 +339,24 @@ impl MeshBuilder {
  {
  let buffers = &mut self.buffer;
  let rect = t::math::rect(bounds.x, bounds.y, bounds.w, bounds.h);
  - let radii = t::basic_shapes::BorderRadii::new_all_same(radius);
  + let radii = t::path::builder::BorderRadii::new(radius);
  let vb = VertexBuilder {
  color: LinearColor::from(color),
  };
  + let mut path_builder = t::path::Path::builder();
  + path_builder.add_rounded_rectangle(&rect, &radii, t::path::Winding::Positive);
  + let path = path_builder.build();
  +
  match mode {
  DrawMode::Fill(fill_options) => {
  let builder = &mut t::BuffersBuilder::new(buffers, vb);
  - let _ = t::basic_shapes::fill_rounded_rectangle(
  - &rect,
  - &radii,
  - &fill_options,
  - builder,
  - );
  + let mut tessellator = t::FillTessellator::new();
  + let _ = tessellator.tessellate_path(&path, &fill_options, builder);
  }
  DrawMode::Stroke(options) => {
  let builder = &mut t::BuffersBuilder::new(buffers, vb);
  - let _ =
  - t::basic_shapes::stroke_rounded_rectangle(&rect, &radii, &options, builder);
  + let mut tessellator = t::StrokeTessellator::new();
  + let _ = tessellator.tessellate_path(&path, &options, builder);
  }
  };
  }
  