Deprecate SynthesizedAnnotation and related methods

Since Spring no longer adds the SynthesizedAnnotation interface to the
JDK dynamic proxy used to synthesize an annotation, this commit
officially deprecates SynthesizedAnnotation and related methods in
RuntimeHintsUtils.

See gh-29041, gh-29054
Closes gh-29053

spring-web/src/main/java/org/springframework/web/bind/annotation/WebAnnotationsRuntimeHintsRegistrar.java

@@ -34,6 +34,7 @@ import org.springframework.stereotype.Controller;
 public final class WebAnnotationsRuntimeHintsRegistrar implements RuntimeHintsRegistrar {
 
 	@Override
+	@SuppressWarnings("deprecation")
 	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 		Stream.of(Controller.class, ControllerAdvice.class, CookieValue.class,
 						CrossOrigin.class, MatrixVariable.class, ModelAttribute.class,