Update the `isAncestorOf` method of SpringConfigurationPropertySources so that legacy names are considered for the system environment. Prior to this commit, binding a property such as `my.camelCase.prop` would detect `MY_CAMELCASE_PROP` but not `MY_CAMEL_CASE_PROP` in the system environment. Fixes gh-14479 Co-authored-by: Phillip Webb <pwebb@pivotal.io>