A Beacon Hill watchdog group yesterday released a report indicating that steep cuts to education and other public services are inevitable in 10 of the state’s most cash-strapped cities to fund the rising cost of health care for their municipal retirees, unless the Legislature enacts changes to their benefit structure. According to the report by the business-backed Massachusetts Taxpayers Foundation, the current unfunded liability for retiree health benefits in these cities is $4.5 billion.