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/src/platform/test/display.rs

@@ -1,12 +1,12 @@
 use anyhow::{Ok, Result};
 
-use crate::{Bounds, DisplayId, GlobalPixels, PlatformDisplay, Point};
+use crate::{Bounds, DevicePixels, DisplayId, PlatformDisplay, Point};
 
 #[derive(Debug)]
 pub(crate) struct TestDisplay {
     id: DisplayId,
     uuid: uuid::Uuid,
-    bounds: Bounds<GlobalPixels>,
+    bounds: Bounds<DevicePixels>,
 }
 
 impl TestDisplay {
@@ -16,7 +16,7 @@ impl TestDisplay {
             uuid: uuid::Uuid::new_v4(),
             bounds: Bounds::from_corners(
                 Point::default(),
-                Point::new(GlobalPixels(1920.), GlobalPixels(1080.)),
+                Point::new(DevicePixels(1920), DevicePixels(1080)),
             ),
         }
     }
@@ -31,7 +31,7 @@ impl PlatformDisplay for TestDisplay {
         Ok(self.uuid)
     }
 
-    fn bounds(&self) -> crate::Bounds<crate::GlobalPixels> {
+    fn bounds(&self) -> crate::Bounds<crate::DevicePixels> {
         self.bounds
     }
 }

crates/gpui/src/platform/test/window.rs

@@ -1,7 +1,8 @@
 use crate::{
-    AnyWindowHandle, AtlasKey, AtlasTextureId, AtlasTile, Bounds, DispatchEventResult,
-    GlobalPixels, Pixels, PlatformAtlas, PlatformDisplay, PlatformInput, PlatformInputHandler,
-    PlatformWindow, Point, Size, TestPlatform, TileId, WindowAppearance, WindowParams,
+    AnyWindowHandle, AtlasKey, AtlasTextureId, AtlasTile, Bounds, DevicePixels,
+    DispatchEventResult, Pixels, PlatformAtlas, PlatformDisplay, PlatformInput,
+    PlatformInputHandler, PlatformWindow, Point, Size, TestPlatform, TileId, WindowAppearance,
+    WindowParams,
 };
 use collections::HashMap;
 use parking_lot::Mutex;
@@ -12,7 +13,7 @@ use std::{
 };
 
 pub(crate) struct TestWindowState {
-    pub(crate) bounds: Bounds<GlobalPixels>,
+    pub(crate) bounds: Bounds<DevicePixels>,
     pub(crate) handle: AnyWindowHandle,
     display: Rc<dyn PlatformDisplay>,
     pub(crate) title: Option<String>,
@@ -78,7 +79,7 @@ impl TestWindow {
         let Some(mut callback) = lock.resize_callback.take() else {
             return;
         };
-        lock.bounds.size = size.map(|pixels| f64::from(pixels).into());
+        lock.bounds.size = size.map(|pixels| (pixels.0 as i32).into());
         drop(lock);
         callback(size, scale_factor);
         self.0.lock().resize_callback = Some(callback);
@@ -107,7 +108,7 @@ impl TestWindow {
 }
 
 impl PlatformWindow for TestWindow {
-    fn bounds(&self) -> Bounds<GlobalPixels> {
+    fn bounds(&self) -> Bounds<DevicePixels> {
         self.0.lock().bounds
     }