NEW YORK — The Giants are going all-Bills. Buffalo offensive coordinator Brian Daboll agreed to be the 20th head coach in franchise history on Friday night, following new Giants GM Joe Schoen from upstate New York to North Jersey. Schoen, the Bills’ assistant GM the past five years, led a search that prioritized fixing a broken offense led by Daniel Jones and improving communication inside the building. Now Daboll, 46, the Giants’ first of six candidates interviewed, is the pick to help the GM address both. Daboll guided Bills 2018 first-round pick Josh Allen from a promising raw quarterback i…