Rewrite DowngradeConstraintsTest class in ServiceHandler

With migration of OpenROADM service models to 10.1, new constraints appeared, and structures of routing-constraints has changed imposing to rewrite more or less the whole DowngradeConstraintsTest and an important part of the DowngradeConstraints classes.

This class is used in a context of service-restoration. In the case hard-constraints can not be satisfied, they are downgraded to soft-constraints. If some soft-constraints already was already existing, they are complemented by the hard-constraints.

Complement the implementation of DowngradeConstraints class to take into acount all 10.1 constraints, and completly rewrite its associated unitary test class.