Feature: Filter outings with a gpx track

**Community discussion about this feature (mandatory)**
Link to where this feature has been validated

**Is your feature request related to a problem? Please describe.**
It's not always easy to find GPX tracks. Many routes and outings don't have GPX tracks.
It would allow to select tracks for different activities (ski/walk), to know when it was done, by who.
And to find variants for each route, or combinations of routes.

**Describe the solution you'd like**
Add a possibility to filter outings with gpx tracks in the "divers" menu.
Best, show tracks on the map.