Ui Anti-aliasing radius setting

## What problem does this solve or what need does it fill?

The UI AA radius should be be configurable I think to allow for fine-tuning

## What solution would you like?

My naive idea was to give the `On` variant of `UiAntiAlias` a `radius: f32` field, then extract the radius, bitcast the float to an int, put it into a `ShaderDefVal` and then bitcast it back again to a float in the shader. This might be a terrible thing to do though.