Draw CGPaths

[MSFTFox]

Implement the drawing functionality for CGPaths. This is done via CGContextAddPath and CGContextStrokePath. Implement any missing CGContextPath APIs.

[DHowett-MSFT]

This is also partly covered by #1238.

[DHowett-MSFT]

Of note: The path will be stored transformed (!), and must be detransformed before draw lest we double transform it.