[Nexthop] Fix MoD ingress-port check on XGS (hw logical port)

[sazeed-nexthop]

Summary

AgentMirrorOnDropStatelessTest.DefaultRouteDrop and .AclDrop fail on Tomahawk5 / XGS, on cold and warm boot. validateMirrorOnDropPacket asserts that the MoD packet's ingress-port equals the FBOSS logical PortID. On XGS the PSAMP ingressPort field actually carries the Broadcom hardware logical port id (the low bits of the SAI port object id), which is a different numbering from the FBOSS PortID.

The failure shows up where the injection port's PortID differs from its hardware logical port. When the first interface port maps PortID 1 -> hw logical port 3, the assertion sees 3 vs 1. Platforms where the two happen to coincide for the injection port pass the old assertion only by coincidence, so ingressPort == PortID was silently fragile.

Fix

Add a per-ASIC ingressPortIsHwLogicalPort() to the MirrorOnDropImpl strategy:

• XGS returns true -> validateMirrorOnDropPacket translates the injection PortID via SwSwitch::getHwLogicalPortId() before comparing. The lookup is wrapped in WITH_RETRIES because the stats-backed mapping can lag a warm boot.
• Tajo returns false -> unchanged; its punt-header ingress-port encoding hasn't been characterized against hardware yet.

On platforms where PortID == hwLogicalPort this returns the same value the old check used (no behavior change); where they differ it returns the real hardware port that the MoD packet carries. This mirrors the translation the DNX path already performs via its source-system-port aggregate.

Test Plan

On a Tomahawk5 / XGS platform, AgentMirrorOnDropStatelessTest.DefaultRouteDrop and .AclDrop now pass on both cold and warm boot (previously failed warm boot with ingressPort 3 vs 1).