Add new methods required for 'COLR' v1 to public API (#59703).

* include/freetype/freetype.h (FT_Get_Color_Glyph_Paint): New method
for retrieving the root paint object for a color glyph by specifying
a glyph ID.
(FT_Get_Paint_Layers): New method for retrieving the layers of a
`PaintColorGlyph`.
(FT_Get_ColorLine_Stops): New method for retrieving the stops of a
color.
(FT_Get_Paint): New method for resolving an `FT_OpaquePaint` into an
`FT_COLR_Paint` object.
3 files changed