ivi-shell: add screen_add_layers test

ivi-shell: add screen_add_layers test

Test adds 3 layers in a screen's render order list.
First, it adds in the order which layers are created.
Later, test cleans the render order list,
and adds layers in reverse order.

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>