Inline transform attribute

[Lassebq]

GTK does not support transform attribute in symbolic icon renderer and the transform tag needs to be inlined (child coordiates should be transformed by the transform matrix)
https://gitlab.gnome.org/GNOME/gtk/-/work_items/8161

Sample svg:

<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16"><g fill="currentColor" transform="matrix(0 -1 -1 0 -413 -83.997)"><rect width="2" height="2" x="-92.997" y="-418" overflow="visible" rx="1" ry="1"/><rect width="2" height="2" x="-92.997" y="-422" overflow="visible" rx="1" ry="1"/><rect width="2" height="2" x="-92.997" y="-426" overflow="visible" rx="1" ry="1"/></g></svg>

Re-saving in inkscape keeps transform. Ungrouping and grouping again is what fixes it.