DATACMNS-867 - Rework utility classes.

Removed the additional methods that reflectively checked for the Stream type and whether a Method instance is a default method. Turned utility classes into interfaces where possible. Make use of Lombok's @UtilityClass where not.

Removed obsolete implementation class in StreamUtils in favor of a lambda.

src/main/java/org/springframework/data/projection/DefaultMethodInvokingMethodInterceptor.java

@@ -57,7 +57,7 @@ public class DefaultMethodInvokingMethodInterceptor implements MethodInterceptor
 
 		Method method = invocation.getMethod();
 
-		if (!org.springframework.data.util.ReflectionUtils.isDefaultMethod(method)) {
+		if (!method.isDefault()) {
 			return invocation.proceed();
 		}