As health care costs rise nationwide, municipalities around the state are revisiting the question of whether to remain self-insured, or to switch to a state-run health insurance program for public employees that might help to cushion the financial blow. Belmont is no exception. “Every year we’ve either formally or informally revisited this and every year the numbers dictated against joining the [Massachusetts Group Insurance Commission],” said Select Board member Elizabeth Dione, before a vote earlier this month to begin the…