[FEA] Add a DAQIRI raw Ethernet to UCX GPU egress example

Is your feature request related to a problem? Please describe.

DAQIRI users need a practical example of receiving raw Ethernet data, processing it with CUDA, and forwarding the result to another GPU-capable system using UCX/UCP over RoCEv2.

Describe the solution you'd like

Add an opt-in two-host example implementing:

Raw data source → DAQIRI raw RX → batched CUDA processing
                → UCX/RoCEv2 → GPU-accessible receiver

The example should demonstrate:

• Receiving and assembling packetized data with DAQIRI.
• Applying representative batched CUDA processing.
• Sending processed payloads through UCX/UCP.
• Receiving into GPU-accessible memory.
• Bounded receiver capacity and overload accounting.
• UCX-only, staged, and complete-pipeline benchmarks.
• A UCX-enabled container, example configurations, and a tutorial modeled after the ResNet50 example.
• Mapped pinned memory support for DGX Spark, while retaining CUDA-device support for other systems.

Describe alternatives you've considered

Using DAQIRI multi-engine support, a DAQIRI UCX engine, custom verbs egress, or host-staged sockets would add unnecessary complexity for an example application.

Additional context

A prototype is available on feat/ucx-gpu-egress-example.

On the two-Spark setup, it delivered and GPU-validated 1.6 million processed payloads at approximately 94.94 Gbit/s, with zero drops, sequence gaps, or validation failures.

Review the prototype on feat/ucx-gpu-egress-example and the existing ResNet50 example first, then map the requested two-host raw-RX, CUDA, UCX/RoCEv2, and GPU-accessible receive flow to the project. Done means an opt-in example with configurations, a UCX-enabled container, tutorial, bounded receiver accounting, and the requested benchmark modes.