Pocatello *****
        By: David ShewardT.R. Knight"I don't know where I live," sighs Eddie, the misbegotten hero of Samuel D. Hunter's deceptively simple yet hugely affecting new play Pocatello, at Playwrights Horizons. This shattering cry of despair is uttered in an even voice by T.R. Knight who plays Eddie with painfully real insight, after he recites a seemingly endless list of local landmarks…