Adapt PCE code for OTN services

Adapt PCE code for OTN services

Allows pce code to calculate paths for OTU4, ODU4 structured for LO-ODU,
10GE and 1GE services, provided that the otn-topology contains correct
information for links and otn-nodes/tp.

- add PceNode interface, and use PceOpticalNode and PceOtnNode as two
different implementations of PceNode interface
- review implementations of chooseTribPort, chooseTribSlots methods in
PostAlogPathValidator

JIRA: TRNSPRTPCE-162 TRNSPRTPCE-201
Signed-off-by: Gilles Thouenon <gilles.thouenon@orange.com>
Co-authored-by: Christophe Betoule <christophe.betoule@orange.com>
Change-Id: Id7105571691e9513dff6ca41cd1287f351f35de9