collab ui: Fix notification windows on external monitors (#9817)

Sharing a project displays a notification (window) on every screen.
Previously there was an issue with the positioning of windows on all
screens except the primary screen.

As you can see here:


![image](https://github.com/zed-industries/zed/assets/53836821/314cf367-8c70-4e8e-bc4a-dcbb99cb4f71)

Now:


![image](https://github.com/zed-industries/zed/assets/53836821/42af9ef3-8af9-453a-ad95-147b5f9d90ba)

@mikayla-maki and I also decided to refactor the `WindowOptions` a bit. 
Previously you could specify bounds which controlled the positioning and
size of the window in the global coordinate space, while also providing
a display id (which screen to show the window on). This can lead to
unusual behavior because you could theoretically specify a global bound
which does not even belong to the display id which was provided.

Therefore we changed the api to this:
```rust
struct WindowOptions {
    /// The bounds of the window in screen coordinates
    /// None -> inherit, Some(bounds) -> set bounds.
    pub bounds: Option<Bounds<DevicePixels>>,

    /// The display to create the window on, if this is None,
    /// the window will be created on the main display
    pub display_id: Option<DisplayId>,
}
```

This lets you specify a display id, which maps to the screen where the
window should be created and bounds relative to the upper left of the
screen.

Release Notes:

- Fixed positioning of popup windows (e.g. when sharing a project) when
using multiple external displays.

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/editor/src/editor_tests.rs

@@ -7304,8 +7304,8 @@ async fn test_following(cx: &mut gpui::TestAppContext) {
         cx.open_window(
             WindowOptions {
                 bounds: Some(Bounds::from_corners(
-                    gpui::Point::new(0_f64.into(), 0_f64.into()),
-                    gpui::Point::new(10_f64.into(), 80_f64.into()),
+                    gpui::Point::new(0.into(), 0.into()),
+                    gpui::Point::new(10.into(), 80.into()),
                 )),
                 ..Default::default()
             },