Refactor transportpce-routing-constraint

Transportpce has internal yang models that are very close to official openROADM ones. As an example, transportpce-routing-constraints.yang is more or less equivalent to openroadm-routing-constraints.yang, but the pce-metric enumeration is specific to transportpce and used in several places in PCE.
Since structure uses in PCE uses transportpce model, and input comes from service models with finally the same strucutre but with different types, there are some dedicated code to convert one type to another.
Such things could be advantageously avoid using directly the official openROADM stucture.
For that, specific things as pce-metric must be moved to a common model for example.
Eventually, pce-metric should be also removed and replaced by equivalent metric from offical openROADM models.