feat: Refactor callback to use transient storage

With this, we don't need the univ3 specific method in the router contract. This should be flexible enough for most protocols that integrate

TODO: is this safe enough??

--- don't change below this line ---
ENG-4411 Took 1 hour 52 minutes

Took 4 minutes

Took 5 minutes

foundry/test/executors/UniswapV4Utils.sol

@@ -8,7 +8,6 @@ library UniswapV4Utils {
         address tokenIn,
         address tokenOut,
         bool zeroForOne,
-        address callbackExecutor,
         UniswapV4Executor.UniswapV4Pool[] memory pools
     ) public pure returns (bytes memory) {
         bytes memory encodedPools;
@@ -22,8 +21,6 @@ library UniswapV4Utils {
             );
         }
 
-        return abi.encodePacked(
-            tokenIn, tokenOut, zeroForOne, callbackExecutor, encodedPools
-        );
+        return abi.encodePacked(tokenIn, tokenOut, zeroForOne, encodedPools);
     }
 }