Update `PropertySourceLoader` so that it no longer needs to deal with
matching multi-document files using the `spring.profile` property. The
loader now simply returns one or more `PropertSource` instances for a
given `Resource`.

All property matching now occurs in the `ConfigFileApplicationListener`.
This allows document processing logic to be contained in a single place,
and allows us to rationalize the algorithm so that negative matching
profiles are processed last.

Fixes gh-12159