Support colored stipples on Cocoa NS (Bug#73384)

Support colored stipples on Cocoa NS (Bug#73384)

On Cocoa builds of NS Emacs, stipples are now rendered
using masked CGImages instead of patterned NSColors so that
stipples now render with color.
* src/nsimage.m ([EmacsImage stippleMask:]): Use a CGImageMask to
store the stipple mask when building for Cocoa.
* src/nsterm.m (ns_maybe_dumpglyphs_background): Perform a masked
fill to draw stipples when building for Cocoa.
(ns_draw_stretch_glyph_string): Perform a masked fill to draw
stipples when building for Cocoa.

(cherry picked from commit 9cbbdcee132588a11dc03c3da371176aaa13927c)