Add a way to change what `menu::Confirm` does in the recent projects modal (#8688)

Follow-up of
https://github.com/zed-industries/zed/issues/8651#issuecomment-1973411072

Zed current default is still to reuse the current window, but now it's
possible to do
```json
"alt-cmd-o": [
  "projects::OpenRecent",
  {
    "create_new_window": true
  }
]
```
and change this.

menu::Secondary confirm does the action with opposite window creation
strategy.

Release Notes:

- Improved open recent projects flexibility: settings can change whether
`menu::Confirm` opens a new window or reuses the old one