QCryptographicHash: don't allocate a Private in hash()

Just create it on the stack, we know the lifetime.

Reduces memory allocations in static hash() from 2 to 1.

Change-Id: Ie0e22b023331da9a6f39c80b4cd1a5c016f63a87
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/tools/qcryptographichash.cpp

@@ -665,9 +665,9 @@ QByteArray QCryptographicHashPrivate::finalize()
 */
 QByteArray QCryptographicHash::hash(QByteArrayView data, Algorithm method)
 {
-    QCryptographicHash hash(method);
+    QCryptographicHashPrivate hash(method);
     hash.addData(data);
-    return hash.result();
+    return hash.finalize();
 }
 
 /*!