Replace priority with @Priority

The new @Priority annotation serves the exact same purpose as
@Event(priority = ...), but should be easier to read in complex handler
declarations. It has to be used in conjunction with the @Event
annotation, not instead of it.

event-bus-core/src/test/java/dev/kske/eventbus/core/CancelTest.java

@@ -39,13 +39,15 @@ class CancelTest implements EventListener {
 		assertEquals(1, hits);
 	}
 
-	@Event(eventType = SimpleEvent.class, priority = 100)
+	@Event(eventType = SimpleEvent.class)
+	@Priority(100)
 	void onSimpleFirst() {
 		++hits;
 		bus.cancel();
 	}
 
-	@Event(eventType = SimpleEvent.class, priority = 50)
+	@Event(eventType = SimpleEvent.class)
+	@Priority(50)
 	void onSimpleSecond() {
 		++hits;
 	}

event-bus-core/src/test/java/dev/kske/eventbus/core/DispatchTest.java

@@ -38,20 +38,22 @@ class DispatchTest implements EventListener {
 		bus.dispatch(new SimpleEvent());
 	}
 
-	@Event(eventType = SimpleEvent.class, priority = 200)
+	@Event(eventType = SimpleEvent.class)
+	@Priority(200)
 	@Polymorphic
 	void onSimpleEventFirst() {
 		++hits;
 		assertTrue(hits == 1 || hits == 2);
 	}
 
-	@Event(eventType = SimpleEvent.class, priority = 150)
+	@Event(eventType = SimpleEvent.class)
+	@Priority(150)
 	static void onSimpleEventSecond() {
 		++hits;
 		assertEquals(3, hits);
 	}
 
-	@Event(priority = 100)
+	@Event
 	void onSimpleEventThird(SimpleEvent event) {
 		++hits;
 		assertEquals(4, hits);