product packages have priority over dimensions

[mrpollo]

this is required so we don't send and extra package previously it would create a package with the default variant attributes and append it to the product packages, this would create in some cases expansive rate results

in some cases: carriers typically would measure the package and pick either the dimensions or the weight (whichever is more expensive) and use that to calculate the rates

[mrpollo]

don't merge this yet I need to redo some of the tests...

I'm also feeling that the whole weight array poop that is going on should be gone from here since we have the splitters on spree_core doing that job already ( splitting packages per weight )... would love input here...