test: consolidate and enrich v2 calldata conversion tests

[fsamier]

Summary

Enriches the v2 calldata conversion test suite to cover all currently implemented display field formats, and consolidates the previously per-format test files into a single parametrized module to reduce boilerplate.

Previously only chainId and tokenTicker had dedicated tests. This adds coverage for every implemented format and folds everything into one file with a small inline descriptor helper, so each case is expressed as just its minimal, format-specific part.

What changed

• New tests/v2/convert/calldata/test_convert_fields.py:
  • Inline helpers (convert_field, assert_serializes_param_type) that build a minimal v2 descriptor from a single display field + signature, run the conversion, and assert the serialized PARAM_TYPE TLV tag.
  • One parametrized test_convert_field covering the homogeneous cases: raw, amount, duration, chainId, tokenTicker, addressName, tokenAmount, nftName, calldata, enum (one test id per format).
  • Small dedicated tests for the genuinely distinct cases: date (timestamp vs blockheight encodings), unit params, tokenTicker native_currencies is None, and tokenAmount token-path resolution.
• Removed test_convert_chain_id.py and test_convert_token_ticker.py (superseded by the consolidated module).

Notes

• v2 input models only coerce string enums (e.g. format) in JSON mode, so the helper validates via model_validate_json.
• addressName requires params to resolve, so its case includes {"types": ["contract"]}.

Validation

• All 15 tests pass.
• ruff and mypy pre-commit hooks pass.