Expose DAPHNE ETH peak descriptor arrays

[marroyav]

Description

No parent issue linked yet.

This PR exposes DAPHNE Ethernet peak descriptor arrays through the
rawdatautils DAPHNE Ethernet unpacker bindings for the FDDAQ v5.5.0 target
environment.

The branch is based directly on the package fddaq-v5.5.0 tag and intentionally
avoids unrelated later develop history. In particular, it avoids carrying the
newer FragmentHeader.status_bits API into this FDDAQ v5.5.0 branch, where
the matching fragment header field is still error_bits.

Target environment:

• FDDAQ release/work area: fddaq-v5.5.0-a9-1
• Package base tag: fddaq-v5.5.0 / v2.6.0
• Tested on: np04-srv-017

Dependencies:

• Depends on the matching fddetdataformats branch
  marroyav/daphneeth-fddaq-v5_5_0, which adds the DAPHNE Ethernet peak
  descriptor API used by this unpacker.

Reviewer test instructions:

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature or enhancement (non-breaking change which adds functionality)
• Optimization (non-breaking change that improves code/performance)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Testing checklist

• Unit tests pass (e.g. dbt-build --unittest)
• Minimal system quicktest passes (pytest -s minimal_system_quick_test.py)
• Full set of integration tests pass (dunedaq_integtest_bundle.sh)
• Python tests pass if applicable (e.g. python -m pytest)
• Pre-commit hooks run successfully if applicable (e.g. pre-commit run --all-files)

Testing performed on np04-srv-017:

• dbt-build -c -j4 passed.
• dbt-build --unittest rawdatautils passed.
• DAPHNE Ethernet decode smoke test passed on run 43950, VD_CathodePDS,
  record (1, 0):
  • source ID 800: 1407 DAPHNEEth frames
  • source ID 801: 1395 DAPHNEEth frames
• Additional decode check with --adc-stats completed successfully and printed
  per-channel DAPHNEAnalysisData summaries.

Minimal system quicktest, full integration tests, separate Python pytest, and
pre-commit were not run.

Further checks

• Code is commented where needed, particularly in hard-to-understand areas
• Code style is correct (dbt-build --lint, and/or see https://dune-daq-sw.readthedocs.io/en/latest/packages/styleguide/)
• If applicable, new tests have been added or an issue has been opened to tackle that in the future.
  (Indicate issue here: # (issue))

dbt-build --lint was not run. No new rawdatautils unit test was added; the
change is covered by the build, existing package unit test, and the real-data
DAPHNE Ethernet decode smoke test listed above.