Use `PooledTransactionVariant` instead of `PooledTransaction` to decode txs from their rlp encodings

With the Fusaka fork, blobs contain cell proofs instead of just proofs for each blob. An EIP-7594 blob sidecar has been introduced which `PooledTransaction` doesn't decode.
It is suggested to use `PooledTransactionVariant` here: https://github.com/paradigmxyz/reth/blob/3a3bc5f795d01209fe565cce4991e19fc8cb52ee/crates/ethereum/primitives/src/lib.rs#L31-L33 to decode txs from the Fusaka fork.
If not changed, we end up with the following errors when trying to decode blob txs in Fusaka.
```
2025-07-02T13:51:19.138629Z INFO received a tx tx_hash=0xedf2b8b4bd0476510eb92e027dcb15203996230c25cf6efed2be82e952052c44
2025-07-02T13:51:19.141289Z INFO in get_tx_with_blobs
2025-07-02T13:51:19.141309Z INFO in decode_enveloped_with_real_blobs
2025-07-02T13:51:19.141327Z ERROR Failed to decode pooled transaction: RlpError(UnexpectedString)
2025-07-02T13:51:19.141358Z ERROR Failed to get tx from pool tx_hash=0xedf2b8b4bd0476510eb92e027dcb15203996230c25cf6efed2be82e952052c44 err=Failed to decode transaction, error: unexpected string
```

Start at get_tx_with_blobs and decode_enveloped_with_real_blobs, then compare the PooledTransactionVariant definition in crates/ethereum/primitives/src/lib.rs with the current pooled-transaction decoding path. Done means Fusaka blob transactions using EIP-7594 cell proofs decode successfully without the reported UnexpectedString error.

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