fix: add missing transaction types in serialization

[xdustinface]

The block serialization needed by the sync rewrite which uses #397 fails for special transactions/coinbase because we don't have segwit support. This is intermediate fix. Im have a PR to fully drop support for it (#400) but its not quite ready and i want to look a bit more into it first once the sync stuff is done.

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Improved handling of special transaction types (AssetUnlock, QuorumCommitment, MnhfSignal, Coinbase) to ensure correct serialization and deserialization during transaction processing.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Expanded special transaction type handling in serialization and deserialization to disable SegWit processing for AssetUnlock, QuorumCommitment, MnhfSignal, and Coinbase transaction types. Updated supporting documentation to reflect the broader scope of non-input transaction types.

Changes

Cohort / File(s)	Summary
SegWit Handling for Special Transaction Types dash/src/blockdata/transaction/mod.rs	Extended Encodable and Decodable implementations to disable SegWit-related processing (have_witness/segwit flag) for AssetUnlock, QuorumCommitment, MnhfSignal, and Coinbase transaction types. Updated comments to clarify rationale for blocking SegWit on these special transaction types.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 Hoppy times with special types so rare,
No SegWit witnesses need they share,
Coinbase, Quorum, Asset too—
Signal strong what Dash should do,
Serialization safe and clean,
Simplest fix we've ever seen! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding missing special transaction types (AssetUnlock, QuorumCommitment, MnhfSignal, Coinbase) to the serialization logic to handle SegWit-related processing correctly.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/block-serilization

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