Implement Arrow-to-Frame Conversion (Deserialization) for Arrow Backend

[arnavdham]

This PR implements the deserialization capability for the Apache Arrow backend, completing the round-trip workflow. It adds support for reconstructing PODIO Frame objects from a single-row slice of an Apache Arrow Table.

Key Features & Changes

• convertTableToFrame API: Introduced a public utility to read and reconstruct a Frame from a specific row of an Arrow Table.
• Auto-generated Readers: Updated cpp_generator.py and generator templates (ArrowMapper.cc.jinja2) to generate deserialization/reader functions for all concrete data model types.
• Complex Type Support: Handles reconstruction of collections, subset collections, vector members, relations/references, and Link Collections.
• Generic Parameters: Reconstructs GenericParameters from the frame_parameters struct column in the Arrow Table.

Testing

• Added comprehensive unit tests in test_arrow_converter.cpp covering:
• Full round-trip (Frame $\rightarrow$ Table $\rightarrow$ Frame) checks.
• Multi-row tables and non-zero row index offset mapping.
• Verification of reconstructed relations, subsets, and parameter maps.

Fixes: #986

BEGINRELEASENOTES

• Add support for Arrow-to-Frame conversion (deserialization) for the Apache Arrow backend to complete the round-trip workflow.
• Introduce the convertTableToFrame API to reconstruct podio::Frame objects from a specific row of an Arrow Table.
• Add support for reconstructing complex types (collections, vector members, relations, subsets) and GenericParameters.

ENDRELEASENOTES

[arnavdham]

@jmcarcell Please take a look.

[jmcarcell]

Can you format the PR to have the text between BEGINRELEASENOTES and ENDRELEASENOTES like in other PRs? We have a script that reads those and puts them in a doc file and commits it when tagging. I could do it myself, but it would be good if you do that for this and other PRs.

[arnavdham]

Can you format the PR to have the text between BEGINRELEASENOTES and ENDRELEASENOTES like in other PRs? We have a script that reads those and puts them in a doc file and commits it when tagging. I could do it myself, but it would be good if you do that for this and other PRs.

Done for this PR. Will follow this for any further PRs as well. Do you want me to do this for already merged PRs as well?

[jmcarcell]

Yes, please, I may have forgotten to say so in other PRs.