lima-memspeed: Added a new 'gpu_copy' workload

This new code creates a texture of the same size as the screen.
And then copies it to screen for each frame, pixel to pixel.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
lima-memspeed: Added new 'fb_blank' and 'fb_scanout' fake workloads

These can be used to keep the screen blanked or active, and also
account the framebuffer scanout bandwidth. Only /dev/fb0 is
supported.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>