Expand the 25PRB RFSim CI scenario to validate two PDU sessions with
PCF-driven QoS rules and deterministic per-flow traffic ports. Update
iperf execution to use `-B`/`-p` from test args.

Changes:
- Update `container_5g_rfsim_u0_25prb.xml` to add dual-session
  validation steps, routing setup, and multi-flow UDP iperf
  for UL/DL with explicit bind/port arguments.
- Change `cls_oaicitest.py` to parse bind/port from
  `iperf_args`, and return a clear error when the iperf client exits non-zero.
- Update `nrue.uicc.2pdu.conf` to configure
  session 2 on `openairinterface` with distinct `nssai_sd` values.
- Extend `5g_rfsimulator/mini_nonrf_config.yaml`
  with PCF endpoints, dual slices, dual DNN entries, and PCF policy paths,
  and disable local PCC rules in SMF.
- Update `5g_rfsimulator_u0_25prb/docker-compose.yaml`
  to add the `oai-pcf` service, mount policy directories, and add ext-dn
  route for the second UE subnet.
- Add PCF policy data files for this scenario, in :
  `policies/policy_decisions/policy_decision.yaml`
  `policies/pcc_rules/pcc_rules.yaml`
  `policies/qos_data/qos_data.yaml`

About the ci-scripts:
Co-authored-by: Robert Schmidt <robert.schmidt@openairinterface.org>
Signed-off-by: Guido Casati <guido.casati@openairinterface.org>