Test: Automation for netsniff-ng packet capture

[MateuszGrabuszynski]

Merge only after #1236 and #1234.

Adds automation capabilities for netsniff-ng packet capture instead of tcpdump. As both should not be executed at once, such option was not added.

• in tests/validation/configs/test_config.yaml added tool in .capture_cfg with following options recognized: tcpdump for tcpdump, netsniff or netsniff-ng for netsniff-ng
• in tests/validation/create_pcap_file/netsniff.py created NetsniffRecorder class based on TcpDumpRecorder that can serve as netsniff-ng capturing process class
• added conditional execution of netsniff-ng packet capture in
  • tests/validation/mtl_engine/GstreamerApp.py,
  • tests/validation/mtl_engine/ffmpeg_app.py
  • and tests/validation/mtl_engine/udp_app.py
• modified comments about configuration collection and modification so they reflect actual situation

TODO:

• Check whether the interface name is always produced properly in the command and fix if needed, then remove FIXME comment

Postponed for further reconsideration due to priority:

• Prepare installation automation for seamless execution
• Eliminate duplication by creating a parent Recorder class interface for capture
• Think if the capture can be done via a fixture with automated (code-less*) test_name generation

*code-less here means without interfering with the test code

[Copilot]

Pull Request Overview

This PR adds automation support for netsniff-ng packet capture alongside existing tcpdump functionality, allowing test configuration to choose between capture tools via a tool parameter. The implementation includes a new NetsniffRecorder class modeled after TcpDumpRecorder and updates test files to support both capture methods.

• Introduces conditional packet capture execution for netsniff-ng across test execution engines
• Adds NetsniffRecorder class for netsniff-ng packet capture automation
• Updates comment consistency to reflect actual configuration behavior rather than just tcpdump

Reviewed Changes

Copilot reviewed 52 out of 53 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
tests/validation/configs/test_config.yaml	Adds tool configuration option for capture method selection
tests/validation/create_pcap_file/netsniff.py	New NetsniffRecorder class implementation for netsniff-ng automation
tests/validation/mtl_engine/RxTxApp.py	Adds netsniff support and fixes dual test interface configuration
tests/validation/mtl_engine/ffmpeg_app.py	Integrates netsniff capture in ffmpeg tests and adds new dual test functions
tests/validation/mtl_engine/GstreamerApp.py	Adds netsniff capture support to GStreamer tests
tests/validation/mtl_engine/udp_app.py	Integrates netsniff capture in UDP application tests
Multiple test files	Updates comments to reflect packet capture configuration rather than tcpdump-specific

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