Add dispatcher threads start

Author: theEvilReaper

src/main/java/net/minestom/testing/EnvImpl.java

@@ -20,6 +20,9 @@ final class EnvImpl implements Env {
     public EnvImpl(ServerProcess process) {
         this.process = process;
 
+        // Start the dispatcher threads if not already started.
+        process().dispatcher().start();
+
         // Use player provider to disable queued chunk sending.
         // Set here to allow an individual test to override if they want.
         process.connection().setPlayerProvider(TestPlayerImpl::new);
@@ -108,4 +111,4 @@ void check() {
             assertTrue(!initialized || called, "Last listener has not been called: " + eventType.getSimpleName());
         }
     }
-}
+}