Add integration tests for invalid P2P sync messages

* Block sync
- [ ] Invalid fields
- [x] Invalid parent
- [ ] Invalid timestamp
- [x] Invalid number
- [x] Invalid author
- [x] Invalid extradata
- [x] Invalid parcelroot
- [x] Invalid stateroot
- [x] Invalid invoiceroot
- [x] Invalid score
- [x] Invalid seal
- [ ] Invalid size
- [ ] Invalid status message scenario
- [ ] Mismatch between block header and body
- [ ] Invalid seal in pow consensus
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* Parcel sync
- [x] Invalid fields
- [x] Invalid fee
- [x] Invalid nonce
- [x] Invalid networkid
- [x] Invalid signature
- [ ] Invalid size

Start by locating the existing integration tests and P2P block- and parcel-sync entry points; the issue names no files or test targets. Cover the unchecked invalid-message cases listed in the issue, including invalid timestamps, sizes, status scenarios, header/body mismatches, and invalid proof-of-work seals. Done means the listed scenarios have integration-test coverage.

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