Add remaining CanvasLayout shapes

[benstigsen]

This adds the following shapes:

• draw_triangle_empty()
• draw_square_empty()
• draw_square_filled()
• draw_circle_empty()
• draw_arc_filled()
• draw_arc_empty()

Slight reordering and organizing as well.

[benstigsen]

V fmt messed it up. It seems like it was actually correct at the draw_circle_empty() fix (593e6c5)