ATHENS, Greece — Greece intends to put forward new bailout proposals to its European partners at an emergency summit today, government sources here said, as officials sought to stave off a collapse of their country’s banking system and its potential ejection from the eurozone. Prime Minister Alexis Tsipras huddled with leaders from across the political spectrum on Monday morning and well into the afternoon to hash out a new bailout plan that they could support as a united front and that would be more palatable to international and European creditors.