CORS support in HTTP header predicate

This commit introduces CORS support for the HeadersPredicate in
WebMvc.fn and WebFlux.fn.

Closes gh-24564

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RequestPredicates.java

@@ -543,7 +543,12 @@ public abstract class RequestPredicates {
 
 		@Override
 		public boolean test(ServerRequest request) {
-			return this.headersPredicate.test(request.headers());
+			if (CorsUtils.isPreFlightRequest(request.servletRequest())) {
+				return true;
+			}
+			else {
+				return this.headersPredicate.test(request.headers());
+			}
 		}
 
 		@Override