Reorder state changes and event emission for consistency (#2719)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

contracts/access/Ownable.sol

@@ -25,9 +25,7 @@ abstract contract Ownable is Context {
      * @dev Initializes the contract setting the deployer as the initial owner.
      */
     constructor() {
-        address msgSender = _msgSender();
-        _owner = msgSender;
-        emit OwnershipTransferred(address(0), msgSender);
+        _setOwner(_msgSender());
     }
 
     /**
@@ -53,8 +51,7 @@ abstract contract Ownable is Context {
      * thereby removing any functionality that is only available to the owner.
      */
     function renounceOwnership() public virtual onlyOwner {
-        emit OwnershipTransferred(_owner, address(0));
-        _owner = address(0);
+        _setOwner(address(0));
     }
 
     /**
@@ -63,7 +60,12 @@ abstract contract Ownable is Context {
      */
     function transferOwnership(address newOwner) public virtual onlyOwner {
         require(newOwner != address(0), "Ownable: new owner is the zero address");
-        emit OwnershipTransferred(_owner, newOwner);
+        _setOwner(newOwner);
+    }
+
+    function _setOwner(address newOwner) private {
+        address oldOwner = _owner;
         _owner = newOwner;
+        emit OwnershipTransferred(oldOwner, newOwner);
     }
 }