Rationalize hints required for annotations

This commit updates RuntimeHintsUtils to focus on registering a JDK
proxy only as annotations of annotated elements that have at least
an introspection hints are visible out-of-the-box.

This commit also removes unnecessary hints and adapt `@Reflective` to
detect if a hint is required using the introduced
MergedAnnotation#isSynthesizable.

See gh-28967

spring-tx/src/main/java/org/springframework/transaction/annotation/TransactionRuntimeHints.java

@@ -37,7 +37,7 @@ class TransactionRuntimeHints implements RuntimeHintsRegistrar {
 
 	@Override
 	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
-		RuntimeHintsUtils.registerAnnotation(hints, Transactional.class);
+		RuntimeHintsUtils.registerSynthesizedAnnotation(hints, Transactional.class);
 		hints.reflection()
 				.registerTypes(List.of(
 								TypeReference.of(Isolation.class),