Use ClutterImage on StTextureCache
EDIT: Looks like this MR is being shared on forums, so here's a small clarification: this MR does not fix slow disks. If you have a spinning hard drive overloaded with IO requests, icons will still take a while to load.
This is a subproduct of my research on moving Mutter and GNOME Shell to use ClutterContent. StTextureCache uses ClutterTexture as the content of an actor. ClutterTexture is a deprecated class, for Clutter's new model is splitting content from actors themselves. Most importantly, this branch prevents creating a lot of textures.
I also found a case where we were unnecessarily creating textures after loading the GdkPixbuf.
Did not measure anything specifically, but it is very noticeable that this MR makes loading icon grid instantaneous, and makes the login animation much smoother.