gpui: Fix text-align with nowrap mode (#24116)

Release Notes:

- N/A


------

- Continue #24090 to fix text align for when used `whitespace_nowrap`.
- Fix wrapped line length calculation.

And add example

```
cargo run -p gpui --example text_layout
```

<img width="760" alt="image"
src="https://github.com/user-attachments/assets/a087c300-0e0e-4a80-98c6-90161a9b0905"
/>

---------

Co-authored-by: Owen Law <owenlaw222@gmail.com>

crates/gpui/examples/text_layout.rs

@@ -0,0 +1,64 @@
+use gpui::{
+    div, prelude::*, px, size, App, Application, Bounds, Context, Window, WindowBounds,
+    WindowOptions,
+};
+
+struct HelloWorld {}
+
+impl Render for HelloWorld {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        div()
+            .bg(gpui::white())
+            .flex()
+            .flex_col()
+            .gap_3()
+            .p_4()
+            .size_full()
+            .child(div().child("Text left"))
+            .child(div().text_center().child("Text center"))
+            .child(div().text_right().child("Text right"))
+            .child(
+                div()
+                    .flex()
+                    .gap_2()
+                    .justify_between()
+                    .child(
+                        div()
+                            .w(px(400.))
+                            .border_1()
+                            .border_color(gpui::blue())
+                            .p_1()
+                            .whitespace_nowrap()
+                            .overflow_hidden()
+                            .text_center()
+                            .child("A long non-wrapping text align center"),
+                    )
+                    .child(
+                        div()
+                            .w_32()
+                            .border_1()
+                            .border_color(gpui::blue())
+                            .p_1()
+                            .whitespace_nowrap()
+                            .overflow_hidden()
+                            .text_right()
+                            .child("100%"),
+                    ),
+            )
+    }
+}
+
+fn main() {
+    Application::new().run(|cx: &mut App| {
+        let bounds = Bounds::centered(None, size(px(800.0), px(600.0)), cx);
+        cx.open_window(
+            WindowOptions {
+                window_bounds: Some(WindowBounds::Windowed(bounds)),
+                ..Default::default()
+            },
+            |_, cx| cx.new(|_| HelloWorld {}),
+        )
+        .unwrap();
+        cx.activate(true);
+    });
+}