Support @⁠TestBean factory methods defined in interfaces

Prior to this commit, @⁠TestBean factory methods were required to be
defined in the test class or one of its superclasses. However, users
may wish to define common factory methods in interfaces that can be
shared easily across multiple test classes simply by implementing the
necessary interface(s).

This commit therefore switches from ReflectionUtils to
MethodIntrospector to find @⁠TestBean factory methods in implemented
interfaces within the type hierarchy of the test class.

Closes gh-32943

spring-test/src/main/java/org/springframework/test/context/bean/override/convention/TestBeanOverrideProcessor.java

@@ -28,6 +28,7 @@ import java.util.Objects;
 import java.util.Set;
 
 import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.core.MethodIntrospector;
 import org.springframework.core.ResolvableType;
 import org.springframework.lang.Nullable;
 import org.springframework.test.context.TestContextAnnotationUtils;
@@ -88,24 +89,23 @@ class TestBeanOverrideProcessor implements BeanOverrideProcessor {
 				supportedNames.contains(method.getName()) &&
 				methodReturnType.isAssignableFrom(method.getReturnType()));
 
-		List<Method> methods = findMethods(clazz, methodFilter);
+		Set<Method> methods = findMethods(clazz, methodFilter);
 		if (methods.isEmpty() && TestContextAnnotationUtils.searchEnclosingClass(clazz)) {
 			methods = findMethods(clazz.getEnclosingClass(), methodFilter);
 		}
 
-		Assert.state(!methods.isEmpty(), () -> """
+		int methodCount = methods.size();
+		Assert.state(methodCount > 0, () -> """
 				Failed to find a static test bean factory method in %s with return type %s \
 				whose name matches one of the supported candidates %s""".formatted(
 						clazz.getName(), methodReturnType.getName(), supportedNames));
 
-		long nameCount = methods.stream().map(Method::getName).distinct().count();
-		int methodCount = methods.size();
-		Assert.state(nameCount == 1, () -> """
+		Assert.state(methodCount == 1, () -> """
 				Found %d competing static test bean factory methods in %s with return type %s \
 				whose name matches one of the supported candidates %s""".formatted(
 					methodCount, clazz.getName(), methodReturnType.getName(), supportedNames));
 
-		return methods.get(0);
+		return methods.iterator().next();
 	}
 
 	@Override
@@ -138,10 +138,8 @@ class TestBeanOverrideProcessor implements BeanOverrideProcessor {
 	}
 
 
-	private static List<Method> findMethods(Class<?> clazz, MethodFilter methodFilter) {
-		List<Method> methods = new ArrayList<>();
-		ReflectionUtils.doWithMethods(clazz, methods::add, methodFilter);
-		return methods;
+	private static Set<Method> findMethods(Class<?> clazz, MethodFilter methodFilter) {
+		return MethodIntrospector.selectMethods(clazz, methodFilter);
 	}