🍒 faces/colorgrid: Replace grid implementation with the one from FaceGrid

This face was copied from an earlier version of FaceGrid. FaceGrid now has an improved implementation that works a lot better in panels etc. Copy that implementation over to ColorGrid so we get the same improvements there.

Ultimately we should get rid of ColorGrid in favour of a simple colored rectangle face that can be placed in FaceGrid, but that's for later.

(cherry picked from commit 10c16397)

Co-authored-by: Arjen Hiemstra ahiemstra@heimr.nl