People have talked about men wearing engagement rings for years, but that “trend” has never really blown up.   But now, the most famous jewelry store in the world is about to validate it.  Tiffany & Co. is rolling out a brand new line of engagement rings for men this month.   They haven’t said what the prices are going to be, but the pictures show the rings look more like men’s wedding bands . . . just with a huge diamond embedded in them. And the metals are titanium and platinum.