G1 doesn't need pre write barrier for stores from new allocated objects

The pre-write barrier of G1 is used to capture the object disconnected from the marking graph which could be unmarked aka *white* and stored into *black* objects then break tri-color invariance. But references in new allocated objects are created in object initialization after marking start and never could be white. So we don't need pre-write barrier for stores from new allocated objects. The same mechanism is also used for barrier eliminantion in GenZGC.