Provide a method to retrieve all singleton autowire candidates from the bean factory

[wilkinsona]

Please see spring-projects/spring-boot#44706 for background. It would be useful to have a method similar to SimpleAutowireCandidateResolver.resolveAutowireCandidates(ConfigurableListableBeanFactory, Class<T>) that only considers singleton beans. The key to addressing spring-projects/spring-boot#44706 is to avoid any attempt to create prototype beans.

[jhoeller]

I ended up exposing the same arguments as for the overloaded getBeanNamesForType/getBeansOfType variant: includeNonSingletons and allowEagerInit.

[jhoeller]

Reopening for an includeNonSingletons variant of ObjectProvider.stream/orderedStream.