Document non-default candidate beans and Java-based configuration of non-autowire candidate beans

[wilkinsona]

Affects: 6.2

As part of https://github.com/spring-projects/spring-boot/issues/22403, I'd like to link to some Spring Framework reference documentation that explains defaultCandidate=false and shows how to use it. Unless the search is failing me, it doesn't appear to be mentioned at all in the reference documentation at the moment.

Something similar for autowireCandidate=false would also be useful for https://github.com/spring-projects/spring-boot/issues/41526. I've found "Excluding a Bean from Autowiring" but it's focused purely on XML configuration.