Keep traces filter state persistent in the browser

When you used the traces filter to make a complicated selection, then until now it was always reset to the default search for all traces when you came navigated to the traces screen. This was more than a mild annoyance and has been replaced with a new behavior where the filter state is always stored in your browser’s local storage. The URL is automatically updated with the stored filter state, so that you can easily copy paste it for a colleague.