Kathryn Hahn has joked about her plethora of “best friend or randy crazy lady” roles in comedies, but recent projects by Jill Soloway (“Afternoon Delight”) and Tamara Jenkins (the new Netflix film “Private Life”) have cast Hahn in the lead role, and suddenly we have an exciting leading lady who’s much more than a scene-stealer-extraordinaire. She lets us in on a fascinating process she has for getting into the “I” of the character and talks about the road that led to “Private Life."