Support `grid::pattern()` / gradient fills

[trevorld]

{ggplot2} 3.5.0 geoms were updated to accept grid.pattern() / gradient fills. The geoms in {ggforce} could also be updated to accept such fills:

• [ ] Bump required ggplot2 version number to v3.5
• [ ] Replace code like fill = alpha(fill, alpha) with fill = ggplot2::fill_alpha(fill, alpha)