Update path description with OpucnTribSlots

Update path description with OpucnTribSlots

- complement transportpce-pathDescription yang model
  with min and max trib-slot in aToZ and zToA directions
- remove trib-port-number and trib-slot-number from
  transportpce-pathDescription yang model and adapt the code
- set the min and max trib-slots in path description to be compliant
  with otn-service-path
- update min and max trib-port and trib-slot calculation wrt
  the different possible rates
- assign them in the correct format OpucnTribSlots (A.B)
- adapt pce400G UT and  func tests accordingly

JIRA: TRNSPRTPCE-477
JIRA: TRNSPRTPCE-478
Signed-off-by: Christophe Betoule <christophe.betoule@orange.com>
Change-Id: I0020d7b539ca89504e4a8a285ef1de1f47c6b064