Fix jellyfin#16308: Community ratings not updating after changing .nfo file.

When "replace all metadata" was issued on a film, with the Web metadata
scrapers and "save to local metadata" disabled, after changing the
.nfo file, 'Community rating' was not updated in the server, remaining
the cached value.

Fixed by adding, in the .nfo parser, an option for
'communityrating' along with value conformity verifiers.

Validation tests were added.

MediaBrowser.Providers/Manager/MetadataService.cs

@@ -806,7 +806,7 @@ namespace MediaBrowser.Providers.Manager
                                 refreshResult.UpdateType |= ItemUpdateType.ImageUpdate;
                             }
 
-                            MergeData(localItem, temp, [], options.ReplaceAllMetadata, true);
+                            MergeData(localItem, temp, [], false, true);
                             refreshResult.UpdateType |= ItemUpdateType.MetadataImport;
 
                             break;