Add support for QoS PCP attributes 9-15

As of April 2026, support for PCP attributes for QoS will become mandatory 
(CIP Volume 2, Edition 1.34 Section 5-7.4.3 "PCP Value Attributes - Attributes 9-15")

Action Items:

1. Implement new QoS instance attributes 9-15 (PCP Attributes)
   1. According to spec, PCP Attributes depend on instance attr 1 (802.1Q Tag Enable which is disable by default): PCP Attributes shall be visible only if attribute 1 is visible.
      Attr 1 is activated via EIP_OBJECT_ENABLE_ATTRIBUTE_REQ.
   2. PCP Attributes are disabled by default.
   3. Host application can activate PCP Attributes via EIP_OBJECT_ENABLE_ATTRIBUTE_REQ
   4. If activated, the PCP Attributes must be settable and getable from host and network.
   5. Nice to have: implement consistency check for activated PCP attributes (depending on activated features: VLAN tagging / Time Sync)
      Maybe use "BUS ON" event to trigger the check?
   6. Just like attr 2-8, the PCP attributes shall take affect not before the next reset/power-cycle.
2. PCP Attributes must be stored in NV memory.
3. When PCP attributes change, we reuse the existing CIPHIL_CMD_NOTIFY_DSCP_CHANGE to notify the change to the time sync object (and PTP Stack).
4. PTP- Stack: PCP values for PTP General and PTP must be configurable. New PTP Command needed (PTP_Control() ). 
   --> Done with PSPTP-120
5. Describe new attributes in API Manual
   1. Add PCP Attributes to QoS instances attribute table.
   2. Describe defaults and how they can be enabled.
   3. Add foot notes for different use cases (VLAN Tagging on/off, Time Sync on/off)
6. Add Migration Note
   1. For existing applications supporting VLAN tagging and/or Time Sync, the new PCP Attributes must be activated.