Skip analysis of non-solution files

Some exercises consist of more than one file in the `src/main/java` folder, and some of them are designed to be read-only files. These are marked as such in the exercise's `.meta/config.json` file, because they should be listed in the `files.editor` list.

For example, the [configuration for the `wizards-and-warriors-2` exercise](https://github.com/exercism/java/blob/main/exercises/concept/wizards-and-warriors-2/.meta/config.json) lists the following files as read-only:

- `src/main/java/Character.java`
- `src/main/java/Destination.java`
- `src/main/java/TravelMethod.java`

The goal of this issue is to make sure that read-only files are never processed by the analyzer.

In most cases processing these files may not introduce any issues, but just in case one of them contains code that triggers an analyzer comment we should skip them by default. If not, a student may receive feedback on a file that they did not write and cannot edit, which is just confusing.

Beginne mit exercises/concept/wizards-and-warriors-2/.meta/config.json und verfolge, wie der Analyzer seine files.editor-Liste liest. Fertig ist die Änderung, wenn dort als schreibgeschützt markierte Dateien von der Analyse ausgeschlossen werden, während bearbeitbare Lösungsdateien weiterhin verarbeitet werden.

Vom Indexierungsmodell aus dem Issue-Text verfasst.