Former Sens. Trent Lott and John Breaux are joining the Washington lobbying firm Crossroads Strategies, a week after Lott was abruptly fired by Squire Patton Boggs. Lott, a Mississippi Republican, and Breaux, a Louisiana Democrat, spent a decade as two of the top lobbyists at Squire Patton Boggs, representing clients such as Nissan, SpaceX and…