Mainline GPUI2 UI work (#3062)

This PR mainlines the current state of new GPUI2-based UI from the
`gpui2-ui` branch.

Release Notes:

- N/A

---------

Co-authored-by: Nate Butler <iamnbutler@gmail.com>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Marshall Bowers <1486634+maxdeviant@users.noreply.github.com>
Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Nate <nate@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/storybook/src/stories/components/buffer.rs

@@ -0,0 +1,34 @@
+use gpui2::geometry::rems;
+use ui::prelude::*;
+use ui::{
+    empty_buffer_example, hello_world_rust_buffer_example,
+    hello_world_rust_buffer_with_status_example, Buffer,
+};
+
+use crate::story::Story;
+
+#[derive(Element, Default)]
+pub struct BufferStory {}
+
+impl BufferStory {
+    fn render<V: 'static>(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        Story::container(cx)
+            .child(Story::title_for::<_, Buffer<V>>(cx))
+            .child(Story::label(cx, "Default"))
+            .child(div().w(rems(64.)).h_96().child(empty_buffer_example()))
+            .child(Story::label(cx, "Hello World (Rust)"))
+            .child(
+                div()
+                    .w(rems(64.))
+                    .h_96()
+                    .child(hello_world_rust_buffer_example(cx)),
+            )
+            .child(Story::label(cx, "Hello World (Rust) with Status"))
+            .child(
+                div()
+                    .w(rems(64.))
+                    .h_96()
+                    .child(hello_world_rust_buffer_with_status_example(cx)),
+            )
+    }
+}