PARIS — The rising price of oil is undermining the European Union’s efforts to rein in Vladimir Putin’s shadow fleet of sanctioned oil tankers. Russian oil is in high demand as the war in the Middle East and tensions around the Strait of Hormuz tighten global supply, sending benchmark crude prices above $100 per barrel on Monday. That risks weakening a central plank of the EU’s efforts to cut off funding for the Russian president’s war in Ukraine: making it harder and more expensive for Moscow