[sfnt] Implement COLR v1 sweep gradients
- freetype.h (FT_PaintSweepGradient): Added FT_PaintSweepGradient to represent a COLR v1 sweep gradient, update format (FT_PaintFormat): Update shifted paint formats, sync with spec.
- sfnt/ttcolr.c (read_paint): Logic to parse sweep gradients, fix struct access in radial gradient implementation.