Eric Swalwell spent years living the high life with campaign donors’ money as a U.S. congressman, staying in five-star hotels and racking up huge bills on fancy dinners and booze. But his luxurious lifestyle also extended to the friendly skies. A former staffer told The Post that Swalwell — whose career imploded this month after allegations of rape and sexual assault — flew “exclusively” first class during his ill-fated run for California governor and his time in Congress.  Campaign reports