Shapes performance

[melonora]

One way we may be able to get a quick improvement on rendering many shapes at once is by not having a face displayed for each shape. Not certain whether when setting face color to a transparent color it would prevent napari to render the face of a shape, but this is worth investigating.

The speed of the lasso tool was vastly improved by not rendering the face when drawing.

[LucaMarconato]

@Czaki you may find this issue useful.