[ upstream commit 7d22d84 ]

[ backporter's notes: extended the same changes to the parsing of
  Endpoint and EndpointSliceV1Beta1 types, whose support had already
  been removed in the main branch. ]

The blamed commit reworked the storage of port information as part of
the k8s.Backends structure, with the goal of reducing allocations.
However, unnamed ports are handled differently, which down the line
broke the propagation of services via clustermesh, when associated
with unnamed ports, as incorrectly ignored.

Let's get this fixed by uniforming the handling, and adding appropriate
filtering to remove the unnamed port entry where appropriate, to
preserve the existing behavior. Additionally, let's extend the service
synchronization script test, to prevent future regressions.

Fixes: 12ae78b ("k8s,loadbalancer: Optimize 'k8s.Backend.Ports' to reduce allocations")
Signed-off-by: Marco Iorio <marco.iorio@isovalent.com>