UX improvement: wallet navigation grouping.

I do a lot of experimenting and use a lot of wallets for that reason:
It'd be nice, in connection with the issue #1882 , to also have the ability to group some wallet in a collapsible way and remember their status (collapsed or not).

For example if you want to monitor a JoinMarket wallet you'll have at least 5 different Specter wallets. One for each Mixed Depth. If you happen for some reason, to want to keep under control via Specter another instance of JM, you'll end up with 10 wallets right there together with all the other ones and making it annoying to navigate/scroll among/through them.

Talking about Join Market, it'd be a nice to have touch to be able to monitor the xpub of the Fidelity Bond :-D which, currently, I believe, is incompatible with Specter because JM uses a non standard script for that. BTW not even Sparrow wallet can do it AFAIK.

Read issue #1882 and inspect the current wallet navigation behavior in the desktop application. Define the grouping interaction and how collapsed or expanded state should be remembered; done means grouped wallets can be collapsed and reopened with their state preserved.

Written by the indexing model from the issue text.