"actuation" was the first Use-Case so historically didn't have its own
Kas file. This has however meant that all subsequent Use-Case kas files
have had to :remove the "actuation" EXTRA_IMAGE_FEATURE before adding
new ones.

For consistency, introduce actuation.yml to add the "actuation"
EXTRA_IMAGE_FEATURE and remove the definition in arm-auto-solutions.yml

Signed-off-by: Peter Hoyes <peter.hoyes@arm.com>