SpringBootMockResolver causes AopTestUtils.getUltimateTargetObject to recurse until the stack overflows when it calls it with Spring Security's authentication manager bean

[sbrannen]

As mentioned in spring-projects/spring-framework#29215 (comment), please consider introducing a custom, defensive variant of AopTestUtils.getUltimateTargetObject() in SpringBootMockResolver to avoid attempting to unwrap proxies backed by a non-static TargetSource.