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/ui/src/components/player_stack.rs

@@ -0,0 +1,66 @@
+use crate::prelude::*;
+use crate::{Avatar, Facepile, PlayerWithCallStatus};
+
+#[derive(Element)]
+pub struct PlayerStack {
+    player_with_call_status: PlayerWithCallStatus,
+}
+
+impl PlayerStack {
+    pub fn new(player_with_call_status: PlayerWithCallStatus) -> Self {
+        Self {
+            player_with_call_status,
+        }
+    }
+
+    fn render<V: 'static>(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        let system_color = SystemColor::new();
+        let player = self.player_with_call_status.get_player();
+        self.player_with_call_status.get_call_status();
+
+        let followers = self
+            .player_with_call_status
+            .get_call_status()
+            .followers
+            .as_ref()
+            .map(|followers| followers.clone());
+
+        // if we have no followers return a slightly different element
+        // if mic_status == muted add a red ring to avatar
+
+        div()
+            .h_full()
+            .flex()
+            .flex_col()
+            .gap_px()
+            .justify_center()
+            .child(
+                div().flex().justify_center().w_full().child(
+                    div()
+                        .w_4()
+                        .h_1()
+                        .rounded_bl_sm()
+                        .rounded_br_sm()
+                        .fill(player.cursor_color(cx)),
+                ),
+            )
+            .child(
+                div()
+                    .flex()
+                    .items_center()
+                    .justify_center()
+                    .h_6()
+                    .px_1()
+                    .rounded_lg()
+                    .fill(if followers.is_none() {
+                        system_color.transparent
+                    } else {
+                        player.selection_color(cx)
+                    })
+                    .child(Avatar::new(player.avatar_src().to_string()))
+                    .children(followers.map(|followers| {
+                        div().neg_mr_1().child(Facepile::new(followers.into_iter()))
+                    })),
+            )
+    }
+}