native/nativesdk: Clean up the depends ordering after bitbake override handling updates

native/nativesdk: Clean up the depends ordering after bitbake override handling updates

This massively cleans up the dependency handling in the two classes
when interacting with BBCLASSEXTEND.

This change has a dependency on the bitbake override handling change
and also the existence of the RecipePreFinalise event.

Signed-off-by: Richard  Purdie <richard.purdie@linuxfoundation.org>