Test status quo for repeatable @PropertySource on composed annotation

This commit introduces tests that verify support for using
@PropertySource as a repeatable annotation without the
@PropertySources container, both locally on an @Configuration class
and on a custom composed annotation.

See gh-26329

spring-context/src/test/resources/org/springframework/context/annotation/p3.properties

@@ -1 +1,2 @@
 testbean.name=p3TestBean
+from.p3=p3Value