Separate circular arc math/approx logic
Separate circular arc math/approx logic

This way we can reuse the math portion for bounding box computation.

smoogipooo/osu-framework,ZLima12/osu-framework,peppy/osu-framework,smoogipooo/osu-framework,ppy/osu-framework,ppy/osu-framework,peppy/osu-framework,ZLima12/osu-framework,ppy/osu-framework,peppy/osu-framework