chore(consensus): OpTxType Conversion (#283)

### Description

Upstreams a small `OpTxType` conversion to `alloy_primitives::U8` from
reth.

---------

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

crates/consensus/src/transaction/tx_type.rs

@@ -1,7 +1,7 @@
 //! Contains the transaction type identifier for Optimism.
 
 use alloy_eips::eip2718::Eip2718Error;
-use alloy_primitives::U64;
+use alloy_primitives::{U64, U8};
 use alloy_rlp::{BufMut, Decodable, Encodable};
 use derive_more::Display;
 
@@ -50,6 +50,12 @@ impl arbitrary::Arbitrary<'_> for OpTxType {
     }
 }
 
+impl From<OpTxType> for U8 {
+    fn from(tx_type: OpTxType) -> Self {
+        Self::from(u8::from(tx_type))
+    }
+}
+
 impl From<OpTxType> for u8 {
     fn from(v: OpTxType) -> Self {
         v as Self