Currently we keep track of 3 command buffers. Data transfer, compute and graphics. The reason is that data transfer and compute commands cannot be recorded in a command buffer that has an active render pass. This PR simplifies the implementation by combining data transfer and compute commands as there is no need to separate those in individual command buffers. This is in preparation of improving submission performance. Pull Request: https://projects.blender.org/blender/blender/pulls/115033