Improve secondary GPU blitting path performance (power draw) by using damage rectangles

meta_renderer_native_gles3_blit_shared_bo used to blit to the secondary GPU currently does not use damage rectangles and always blits the whole frame to the secondary GPU. This function could benefit from taking the damage rectangles functions higher up already have and applying them to reduce the amount of blitting happening. This can both improve performance and reduce power draw on secondary GPUs.

See also #3461 (comment 2234151) for details.

This was extracted from #3461 to not lose track of this improvement.