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

assets/keymaps/default-linux.json

@@ -343,6 +343,13 @@
   {
     "context": "Workspace",
     "bindings": {
+      // Change the default action on `menu::Confirm` by setting the parameter
+      // "alt-cmd-o": [
+      //     "projects::OpenRecent",
+      //     {
+      //         "create_new_window": true
+      //     }
+      // ]
       "ctrl-alt-o": "projects::OpenRecent",
       "ctrl-alt-b": "branches::OpenRecent",
       "ctrl-~": "workspace::NewTerminal",