refactor(vertex-parser): Move serialization and deserialization to vertex parser module

[msbrogli]

Motivation

This refactor extracts all binary serialization and deserialization into a dedicated hathor/transaction/vertex_parser/ package, turning vertex classes into pure data containers that delegate to the parser module.

Acceptance Criteria

• All binary serialization/deserialization for vertices (blocks, transactions, token creation, on-chain blueprints, PoA blocks) is handled by dedicated modules under
  hathor/transaction/vertex_parser/, organized by vertex type (_block.py, _transaction.py, _token_creation.py, _on_chain_blueprint.py, _common.py)
• Header serialization/deserialization (NanoHeader, FeeHeader) is extracted into _nano_header.py, _fee_header.py, and _headers.py within the vertex parser package
• A unified public API module (vertex_serializer.py) exposes top-level functions (serialize, serialize_funds, serialize_graph, serialize_sighash, get_sighash_data, etc.) that
  route to the appropriate type-specific serializer based on TxVersion
• Model classes (Block, Transaction, TokenCreationTransaction, etc.) retain their get_funds_struct(), get_graph_struct(), create_from_struct(), and get_sighash_all() methods
  but delegate to the vertex parser functions rather than implementing serialization inline
• TxInput and TxOutput serialization (bytes, get_sighash_bytes, create_from_bytes) delegates to the vertex parser
• The former hathor/transaction/vertex_parser.py file is renamed to _vertex_parser.py inside the new package, preserving the VertexParser class and its import path via
  init.py

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[github-actions]

Bencher Report

Branch	refactor/vertex-parser-package
Testbed	ubuntu-22.04

Click to view all benchmark results

Benchmark	Latency	Benchmark Result minutes (m) (Result Δ%)	Lower Boundary minutes (m) (Limit %)	Upper Boundary minutes (m) (Limit %)
sync-v2 (up to 20000 blocks)	📈 view plot 🚷 view threshold	1.59 m (-7.15%) Baseline: 1.71 m	1.54 m (96.93%)	2.05 m (77.37%)

🐰 View full continuous benchmarking report in Bencher

[codecov]

Codecov Report

❌ Patch coverage is 87.13318% with 114 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@9d036e3). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...hor/transaction/vertex_parser/vertex_serializer.py	77.32%	31 Missing and 8 partials ⚠️
hathor/transaction/vertex_parser/_nano_header.py	74.71%	11 Missing and 11 partials ⚠️
...r/transaction/vertex_parser/_on_chain_blueprint.py	62.50%	9 Missing and 9 partials ⚠️
hathor/transaction/base_transaction.py	56.52%	10 Missing ⚠️
hathor/transaction/vertex_parser/_block.py	85.71%	4 Missing and 4 partials ⚠️
hathor/transaction/vertex_parser/_headers.py	87.93%	4 Missing and 3 partials ⚠️
hathor/transaction/merge_mined_block.py	84.21%	3 Missing ⚠️
hathor/nanocontracts/on_chain_blueprint.py	93.33%	1 Missing and 1 partial ⚠️
...athor/transaction/vertex_parser/_token_creation.py	97.43%	2 Missing ⚠️
hathor/transaction/vertex_parser/_transaction.py	96.22%	1 Missing and 1 partial ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1597   +/-   ##
=========================================
  Coverage          ?   85.58%           
=========================================
  Files             ?      449           
  Lines             ?    33946           
  Branches          ?     5309           
=========================================
  Hits              ?    29051           
  Misses            ?     3872           
  Partials          ?     1023           

Flag	Coverage Δ
test-lib	85.58% <87.13%> (?)

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