Add test contracts for storage layout

using structure types

tests/check-upgradeability/contractV1_struct.sol

@@ -0,0 +1,8 @@
+contract ContractV1{
+    struct Foo {
+        uint256 bar;
+        address baz;
+    }
+    address destination;
+    Foo foo;
+}

tests/check-upgradeability/contractV2_struct.sol

@@ -0,0 +1,8 @@
+contract ContractV2{
+    struct Foo {
+        uint256 bar;
+        address baz;
+    }
+    address destination;
+    Foo foo;
+}

tests/check-upgradeability/contractV2_struct_bug.sol

@@ -0,0 +1,8 @@
+contract ContractV2{
+    struct Foo {
+        uint8 bar;
+        address baz;
+    }
+    address destination;
+    Foo foo;
+}