dpdk: move RSS configuration into port configuration

[SiskaPavel]

Summary

Fix RSS configuration with i40e and multiple RX queues

Details

Issue #313 was reproduced on an identical NIC in our lab. When multiple RX queues are configured with the i40e driver, the default RSS configuration (RTE_ETH_RSS_IP) does not distribute packets correctly, sometimes resulting in Errno:-22.
By default, the plugin now falls back to using NIC/driver-provided RSS (rss_offload: null). Users can explicitly override RSS using the rss_offload parameter, though this is experimental and may lead to uneven RX queue distribution.

Additional notes
When only a single RX queue is used, RSS is effectively disabled, and all packets are received on that single queue.

✅ Checks

• Relevant documentation was updated (if needed)
• CI pipeline passes (build, tests, lint, static analysis)
• New code follows clang-tidy rules
• The change is clearly related to a specific issue / requirement
• Documentation (e.g. Doxygen) is updated if needed
• The PR is rebased on the latest master
• No unrelated changes are included

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