Update `AnnotationsPropertySource` so that nested annotations are
supported. Prior to this commit, annotations annotated with
`@PropertyMapping` that contained nested annotation attributes would
result in instances of `TypeMappedAnnotation` being used as properties.
This usually led to errors due to not being able to convert those to
Strings. This commit makes it so that nested annotations are recursively
mapped to properties. This should allow for more complex configuration
to be mapped from annotations.

See gh-23146