WASHINGTON — President Trump’s White House counterterrorism director Sebastian Gorka told The Post that he believes China intentionally flooded the United States with fentanyl in a present-day “Opium War” designed to weaken America through the “targeted killing” of its citizens. Gorka unloaded the blistering assessment Monday in a “Pod Force One” interview with The Post’s Miranda Devine — before Trump departed Tuesday afternoon for a state visit to Beijing that is expected to focus on trade