Improve track delete UI

[oskarrough]

To delete a track you

1. Open the contextual menu
2. Click "Delete"
3. Click the checkbox (label isn't linked (:)
4. Click "Delete track"

It's a bit much with four clicks. I think we do need to ask for confirmation, but clicking delete twice should be enough. Skip the checkbox.

1. Open the contextual menu
2. Click "Delete"
3. Click "Delete track"

Note that for deleting a channel, we might want to keep the checkbox. So the form component, can't remember how it works, should be able to work with and without confirmation checkbox.

[oskarrough]

I removed it from <r4-track-form> here https://github.com/radio4000/components/commit/5d374f52f8b7d9340afc31fa5e7f863f16a498c8. Instead of making it optional, I thought we can just add it back, if we ever need it.