When we draw SVG icons we have an optional argument that specifies to
treat it as multicolor. This PR allows doing the same thing when
requesting a bitmap from an icon. This is only currently done for
Dialog boxes and the About screen. The purpose of this isn't really
to allow multicolor dialog icons, but to get to the point where a
single SVG source file could be used as monochrome (changing the one
color with text color) or multi-color (changing internal colors with
themes) without needing multiple copies of the source file
Pull Request: https://projects.blender.org/blender/blender/pulls/126193
30038f1710