Cleanup: Split gpu_texture_image.c into BKE and IMB modules

This is in order to disolve GPU_draw.h into more meaningful code blocks.

All the Image related function are in `image_gpu.c`.
All the MovieClip related function are in `movieclip.c`.

The IMB module now has a connection with GPU. This is not strickly
necessary and the code could be move to `image_gpu.c` if needed.

The Image garbage collection is also ported to `image_gpu.c`.

source/blender/draw/engines/eevee/eevee_engine.c

@@ -32,6 +32,8 @@
 
 #include "DNA_world_types.h"
 
+#include "IMB_imbuf.h"
+
 #include "eevee_private.h"
 
 #include "eevee_engine.h" /* own include */