Surround operation with unchecked to use wrapping arithmetic

https://docs.soliditylang.org/en/v0.8.0/control-structures.html#checked-or-unchecked-arithmetic

packages/contracts/contracts/libraries/rlp/Lib_RLPReader.sol

@@ -592,18 +592,20 @@ library Lib_RLPReader {
         }
 
         // Pick out the remaining bytes.
-        uint256 mask = 256 ** (32 - (_length % 32)) - 1;
-        assembly {
-            mstore(
-                dest,
-                or(
-                    and(mload(src), not(mask)),
-                    and(mload(dest), mask)
+        unchecked {
+            uint256 mask = 256 ** (32 - (_length % 32)) - 1;
+            assembly {
+                mstore(
+                    dest,
+                    or(
+                        and(mload(src), not(mask)),
+                        and(mload(dest), mask)
+                    )
                 )
-            )
-        }
+            }
 
-        return out;
+            return out;
+        }
     }
 
     /**

packages/contracts/contracts/libraries/rlp/Lib_RLPWriter.sol

@@ -228,11 +228,13 @@ library Lib_RLPWriter {
             src += 32;
         }
 
-        uint256 mask = 256 ** (32 - len) - 1;
-        assembly {
-            let srcpart := and(mload(src), not(mask))
-            let destpart := and(mload(dest), mask)
-            mstore(dest, or(destpart, srcpart))
+        unchecked {
+            uint256 mask = 256 ** (32 - len) - 1;
+            assembly {
+                let srcpart := and(mload(src), not(mask))
+                let destpart := and(mload(dest), mask)
+                mstore(dest, or(destpart, srcpart))
+            }
         }
     }