snapshot: Reorder color matrix nodes containing a transform node

snapshot: Reorder color matrix nodes containing a transform node

A color matrix node that contains a transform node can also be expressed
the other way around, as a transform node containing a color matrix
node.

In the general case, the color matrix node will have to draw its
child to a texture so it can color every pixel of that texture, but the
renderers can short-cut this if the child of the color matrix node is
already a texture node. So if we have a node tree like

Color Matrix
    - Transform
        - Texture

The renderer would have to either check the grandchild of the color
matrix or simply fall back to rendering the transform node to a texture.

In the new configuration:

Transform
    - Color Matrix
        - Texture

The renderer can easily see that the child node of the color matrix node
is a texture, and skip rendering it to a texture.

This is for example happening in current Adwaita for spinners, which are
rotated symbolics.