Remove support for arbitrary extension for `--config-path` and `BIOME_CONFIG_PATH`. We should handle only `.json` and `.jsonc` and emit an error otherwise.

At the moment, a command like the following is *accepted*:

```bash
biome --config-path=file.yml
```

The `file.yml` gets interpreted as a JSON/JSONC file, which is incorrect. The task is to reject such cases. 