Revert "copy Symfony DI YamlFileLoader and set private access modfiers to protected"
Even though I dont agree on the design of YamlFileLoader, copy paste is much worse.
This reverts commit c4a2d248970ee891ee6734c5edc813384b004f4d.
DrupalModuleHookLoader making place for YamlArrayLoader fixes copy paste YamlFileLoader