Simplify poseidon usage

[illuzen]

shouldn't change any hashes, but simplifies Header definition

depends on the new qp-poseidon PR Quantus-Network/qp-poseidon#74

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Note

High Risk
Changes block header typing and Poseidon dependency wiring across runtime and consensus-critical qp-header; a wrong hash would fork the chain despite the stability test.

Overview
This PR drops the qp-poseidon crate from the workspace and standardizes on qp-poseidon-core 2.0.2 (workspace Cargo.toml / lockfile), removing that dependency from node, runtime, wormhole, mining-rewards, dilithium-crypto, and related crates.

qp_header::Header is simplified from Header<Number, BlockHashHasher, StateHasher> to Header<Number, Hashing>: header fields and block hash are H256, Poseidon block hashing is implemented via qp_poseidon_core inside qp-header, and the lone type parameter is the state trie / extrinsics root hasher (still BlakeTwo256 at runtime). Runtime and mocks now use Header<BlockNumber, BlakeTwo256> instead of PoseidonHasher + Blake2.

pallet-wormhole no longer depends on ToFelts / qp_poseidon for config bounds (native balance, asset id, transfer count, wormhole account id). Tests use BlakeTwo256 for TestExternalities instead of PoseidonHasher.

A consensus regression guard replaces the old dual-path hash comparison: poseidon_header_hash_is_stable asserts a fixed devnet header hash (b7dbfd39…).

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