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/gpui/examples/animation.rs

@@ -63,7 +63,7 @@ fn main() {
         .with_assets(Assets {})
         .run(|cx: &mut AppContext| {
             let options = WindowOptions {
-                bounds: Some(Bounds::centered(size(px(300.), px(300.)), cx)),
+                bounds: Some(Bounds::centered(None, size(px(300.), px(300.)), cx)),
                 ..Default::default()
             };
             cx.open_window(options, |cx| {

crates/gpui/examples/hello_world.rs

@@ -23,7 +23,7 @@ impl Render for HelloWorld {
 
 fn main() {
     App::new().run(|cx: &mut AppContext| {
-        let bounds = Bounds::centered(size(px(600.0), px(600.0)), cx);
+        let bounds = Bounds::centered(None, size(px(600.0), px(600.0)), cx);
         cx.open_window(
             WindowOptions {
                 bounds: Some(bounds),

crates/gpui/examples/window_positioning.rs

@@ -0,0 +1,66 @@
+use gpui::*;
+
+struct WindowContent {
+    text: SharedString,
+}
+
+impl Render for WindowContent {
+    fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+        div()
+            .flex()
+            .bg(rgb(0x1e2025))
+            .size_full()
+            .justify_center()
+            .items_center()
+            .text_xl()
+            .text_color(rgb(0xffffff))
+            .child(self.text.clone())
+    }
+}
+
+fn main() {
+    App::new().run(|cx: &mut AppContext| {
+        // Create several new windows, positioned in the top right corner of each screen
+
+        for screen in cx.displays() {
+            let options = {
+                let popup_margin_width = DevicePixels::from(16);
+                let popup_margin_height = DevicePixels::from(-0) - DevicePixels::from(48);
+
+                let window_size = Size {
+                    width: px(400.),
+                    height: px(72.),
+                };
+
+                let screen_bounds = screen.bounds();
+                let size: Size<DevicePixels> = window_size.into();
+
+                let bounds = gpui::Bounds::<DevicePixels> {
+                    origin: screen_bounds.upper_right()
+                        - point(size.width + popup_margin_width, popup_margin_height),
+                    size: window_size.into(),
+                };
+
+                WindowOptions {
+                    // Set the bounds of the window in screen coordinates
+                    bounds: Some(bounds),
+                    // Specify the display_id to ensure the window is created on the correct screen
+                    display_id: Some(screen.id()),
+
+                    titlebar: None,
+                    focus: false,
+                    show: true,
+                    kind: WindowKind::PopUp,
+                    is_movable: false,
+                    fullscreen: false,
+                }
+            };
+
+            cx.open_window(options, |cx| {
+                cx.new_view(|_| WindowContent {
+                    text: format!("{:?}", screen.id()).into(),
+                })
+            });
+        }
+    });
+}