[Group layer] Improve group layer behaviour

[bruhnild]

• [ ] Group layer should be opened if containing a layer activated by default
• [ ] Make sure that when sharing a link with a layer activated the layer group is opened
• [ ] The first sub-group of the view should be opened by default

Current behaviour

https://scotenaction.fedescot.org/visualiser/explorer#layers=870bc8c339d453cd479f9514e98dc09d

Wanted behaviour