Improve URL handling for tracking

The URL is now updated for tracked events. For HTTP error events the URL of the failed request is used instead of the client route. The HTTP status code is now set as event name instead of setting it as value. The unreliable statusText is no longer used. It falls back to OK which doesn't make sense for errors. Furthermore, the room ID is now always replaced with a placeholder.

Index numbers and group names are now also replaced with placeholders. The existing regular expressions have been made slightly more specific.