feat: Remove special handling of the Univ4 callback

The problem was that the pool manager was expecting an ABI encoded result to be returned and we were not returning that (we were returning just a result)
Special thanks to Max for figuring this out

Took 31 minutes

foundry/src/Dispatcher.sol

@@ -127,7 +127,9 @@ contract Dispatcher {
             tstore(_CURRENTLY_SWAPPING_EXECUTOR_SLOT, 0)
         }
 
-        // this is necessary because the delegatecall will prepend extra bytes we don't want like the length and prefix
+        // The final callback result should not be ABI encoded. That is why we are decoding here.
+        // ABI encoding is very gas expensive and we want to avoid it if possible.
+        // The result from `handleCallback` is always ABI encoded.
         bytes memory decodedResult = abi.decode(result, (bytes));
         return decodedResult;
     }