SHARM EL-SHEIKH, Egypt — Arab leaders meeting this weekend in this Egyptian Red Sea resort are moving closer than ever to creating a joint Arab military force, a sign of a new determination among Saudi Arabia, Egypt and their allies to intervene aggressively in regional hotspots, whether against Islamic militants or spreading Iranian power. Creation of such a force has been a longtime goal that has eluded Arab nations in the 65 years since they signed a rarely used joint defense pact.