Checks if a permission string allows the requested operation(s).
| perm |
Permission string (e.g., "rwx", "r--", "---", "???") |
| operation |
Operation type(s) (can be combined with |, e.g., READ | WRITE) |
|
PermissionResult.YES if all operations allowed, PermissionResult.NO if any denied, PermissionResult.ASK if unknown |