gpui: Improve window.prompt to support ESC with non-English cancel text on macOS (#29538)

Release Notes:

- N/A

----

The before version GPUI used `Cancel` for cancel text, if we use
non-English text (e.g.: "取消" in Chinese), then the press `Esc` to cancel
will not work.

So this PR to change it by use `PromptButton` to instead the `&str`,
then we can use `PromptButton::cancel("取消")` for the `Cancel` button.

Run `cargo run -p gpui --example window` to test.

---

Platform Test:

- [x] macOS
- [x] Windows
- [x] Linux (x11 and Wayland)

---------

Co-authored-by: Mikayla Maki <mikayla@zed.dev>
Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

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

@@ -1,8 +1,8 @@
 use crate::{
     AnyWindowHandle, BackgroundExecutor, ClipboardItem, CursorStyle, DevicePixels,
     ForegroundExecutor, Keymap, NoopTextSystem, Platform, PlatformDisplay, PlatformKeyboardLayout,
-    PlatformTextSystem, ScreenCaptureFrame, ScreenCaptureSource, ScreenCaptureStream, Size, Task,
-    TestDisplay, TestWindow, WindowAppearance, WindowParams, size,
+    PlatformTextSystem, PromptButton, ScreenCaptureFrame, ScreenCaptureSource, ScreenCaptureStream,
+    Size, Task, TestDisplay, TestWindow, WindowAppearance, WindowParams, size,
 };
 use anyhow::Result;
 use collections::VecDeque;
@@ -165,10 +165,10 @@ impl TestPlatform {
         &self,
         msg: &str,
         detail: Option<&str>,
-        answers: &[&str],
+        answers: &[PromptButton],
     ) -> oneshot::Receiver<usize> {
         let (tx, rx) = oneshot::channel();
-        let answers: Vec<String> = answers.iter().map(|&s| s.to_string()).collect();
+        let answers: Vec<String> = answers.iter().map(|s| s.label().to_string()).collect();
         self.background_executor()
             .set_waiting_hint(Some(format!("PROMPT: {:?} {:?}", msg, detail)));
         self.prompts