When copying multiple regions that have the same image subresource we are
effectively copying various rects across the same layer range, so we can
batch together all the rects to copy for each layer in a single job.

This allows us to significantly reduce CPU overhead when recording the
command, as we need to produce less jobs and allocate less descriptor
sets. It also offers smaller gains in execution time due to the reduced
job count.

A stress test where we copy 10 subrects of an image in a loop 100 time,
choosing regions that will involve the texel buffer path, we get these
results:

                  | Recording Time | Execution Time |
        ----------|----------------|----------------|
        master    |     3.021s     |    0.112s      |
        ----------|----------------|----------------|
        patch     |     0.163s     |    0.080s      |
        ----------|----------------|----------------|

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <mesa!7782>