Release memory from loaded buffers and textures in Dragon render aspect

Once textures and buffers are loaded, their results are passed on to the Renderer where they are subsequently uploaded to the GPU. If all goes well, there is no reason to hold on to the data in CPU memory.

This could be fixed by overwriting the loaded buffers with empty data in the subsequent calls to the jobs that load the buffers. However, this should be done with some care, to make sure that data is never attempted uploaded later in the Renderer.