This adds a Glyf outline decoder and rasterizer.
So it turns out that FreeType and CoreText have very shitty APIs for raw
Glyf table rasterization. CoreText as far as I can find can't do it at
all. In both cases you have to create a synthetic font with just this
entry and rasterize the glyph. And the code to do all that was WAYYYYYY
complex such that this made way more sense.
We need this for the Glyph Protocol.
**AI disclosure:** Hand-written parser, rasterizer. AI assisted
validation and test writing. I read the spec myself.
cc @qwerasd205
8fcead00e5