Although it's unlikely that the implementation of getPropertySources()
in a ConfigurableEnvironment would be overridden to return a different
MutablePropertySources instance than the one that the
ConfigurableEnvironment typically acts on, it is in fact possible.
In light of that possibility, this commit refactors
ConfigurableEnvironmentPropertySource so that it always obtains a fresh
PropertySources reference.
See gh-34861
7135527765