Add internal functions _getInitializedVersion and _isInitializing (#3598)

contracts/mocks/InitializableMock.sol

@@ -13,6 +13,10 @@ contract InitializableMock is Initializable {
     bool public onlyInitializingRan;
     uint256 public x;
 
+    function isInitializing() public view returns (bool) {
+        return _isInitializing();
+    }
+
     function initialize() public initializer {
         initializerRan = true;
     }
@@ -75,6 +79,10 @@ contract ChildConstructorInitializableMock is ConstructorInitializableMock {
 contract ReinitializerMock is Initializable {
     uint256 public counter;
 
+    function getInitializedVersion() public view returns (uint8) {
+        return _getInitializedVersion();
+    }
+
     function initialize() public initializer {
         doStuff();
     }

contracts/proxy/utils/Initializable.sol

@@ -135,4 +135,18 @@ abstract contract Initializable {
             emit Initialized(type(uint8).max);
         }
     }
+
+    /**
+     * @dev Internal function that returns the initialized version. Returns `_initialized`
+     */
+    function _getInitializedVersion() internal view returns (uint8) {
+        return _initialized;
+    }
+
+    /**
+     * @dev Internal function that returns the initialized version. Returns `_initializing`
+     */
+    function _isInitializing() internal view returns (bool) {
+        return _initializing;
+    }
 }