TEL AVIV, Israel — Tens of thousands of Israelis gathered in central Tel Aviv on Saturday night to protest plans by Prime Minister Benjamin Netanyahu’s new government to overhaul the legal system and weaken the Supreme Court — a step that critics say will destroy the country’s democratic system of checks and balances. “They are trying to destroy the checks and balances of the Israeli democracy. No major unrest was reported, though Israeli media said small crowds scuffled with police as they tried to block a Tel Aviv highway.