They’re drained by the loneliness epidemic, turned off by insanely high restaurant prices — and extremely over the Big Apple’s messy dating scene. Meet the growing group of in-the-know New Yorkers cleverly saying “check, please!” to the status quo — instead finding sustenance and community at intimate, underground dinner parties. From cozy Upper East Side penthouse soirées where martinis clink over truffle risotto, to better-weather Bed-Stuy backyard hangs buzzing with laughter among ornate