Spring Stop using SpringFactoriesLoader.loadFactoryNames in the TestContext framework

AbstractTestContextBootstrapper.getDefaultTestExecutionListenerClassNames() is currently the only remaining use of SpringFactoriesLoader.loadFactoryNames() in the core Spring Framework.

Since SpringFactoriesLoader.loadFactoryNames() will be deprecated in #27954, we should stop using it and remove the getDefaultTestExecutionListenerClassNames() method from AbstractTestContextBootstrapper.

We should likely remove getDefaultTestExecutionListenerClasses() as well and refactor getTestExecutionListeners() to make use of the new FailureHandler support in SpringFactoriesLoader.

Comment From: sbrannen

Since getDefaultTestExecutionListenerClassNames() and getDefaultTestExecutionListenerClasses() are both protected methods and therefore part of the "public" API for anyone extending AbstractTestContextBootstrapper (see https://github.com/spring-projects/spring-framework/issues/27954#issuecomment-1160646333), we could potentially deprecate those two methods in 5.3.x.

@jhoeller & @snicoll, thoughts?