WEST CALDWELL, N.J. — It was a battle down the stretch at the Mizuho Americas Open.  With just a few holes to play, Jeeno Thitikul’s lead over Ruoning Yin dwindled to just a stroke. Yet, respectfully, there was hardly any doubt about who would come out on top at Mountain Ridge Country Club.  Ruoning Yin, a major champion, of which Thitikul is not, bogeyed the par-3 16th. And a group behind, Thitikul birdied the same hole. That gave her a three-shot cushion with two to play.  Thitikul, the world No. 2, would inevitably hoist the trophy, closing with a long birdie putt to successfully defend her Mizuho title. And the past two weeks, it was world No. 1 Nelly Korda who claimed victories.  They are the faces of women’s golf—and it’s the rivalry women’s golf needs. Thitikul, 23, has two wins this year and was the tour’s season-long champion last year .…