[Config] Add possibility to get "parent bundle resource file" in import file loading process

FileLoader doesn't throw FileLoaderImportCircularReferenceException anymore if another file matchs import request.

Currently if a Bundle is defined as child of another Bundle and if we try to import a Resource from parent Bundle into the same "overrided" Resource, we get a FileLoaderImportCircularReferenceException.

Now, FileLoader locates "available files" and try to import one of them (rule is "the first that is not currently loading").

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        |