Costner and Jewel have been romantically linked in the media following the “Yellowstone” actor’s split from ex-wife Christine Baumgartner. Despite months of media speculation over the nature of their relationship, Kevin Costner insists he and Jewel are not dating. Appearing on “The Howard Stern Show” Tuesday, Costner said he and Jewel have had “tremendous conversations” in recent months, but clarified, …