BeanPostProcessor architecture rules do not work with external classes

[philwebb]

As discovered by @nosan, our bean post processor rules don't work for classes that we don't own.

For more details and a potential fix see #45186 (comment)

[mhalbritter]

Hey @nosan, could you please open a PR with those changes so that we can review it? Thanks!

[nosan]

Hey @mhalbritter
PR has been created. I used a slightly different approach.

[philwebb]

Closing in favor of PR #45202. Thanks @nosan!