Merge pull request #11939 from ethereum/userdefined-types-mapping-key

Allow Mapping keys to have type UserDefinedValueType.

test/libsolidity/semanticTests/userDefinedValueType/mapping_key.sol

@@ -0,0 +1,18 @@
+type MyInt is int;
+contract C {
+    mapping(MyInt => int) public m;
+    function set(MyInt key, int value) external {
+        m[key] = value;
+    }
+    function set_unwrapped(int key, int value) external {
+        m[MyInt.wrap(key)] = value;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// set(int256,int256): 1, 1 ->
+// m(int256): 1 -> 1
+// set_unwrapped(int256,int256): 1, 2 ->
+// m(int256): 1 -> 2
+// m(int256): 2 -> 0