Remove old ui and storybook crates (#3125)

This PR deletes the old `ui` and `storybook` crates in favor of their
newer variants that we'll be landing to `main` in the near future.

### Motivation

These crates are based off the old version of GPUI 2 (the `gpui2`
crate).

At this point we have since transitioned to the new version of GPUI 2
(the `gpui3` crate, currently still on the `gpui2` branch).

Having both copies around is confusing, so the old ones are going the
way of the dinosaurs.

Release Notes:

- N/A

crates/ui/src/components/facepile.rs

@@ -1,28 +0,0 @@
-use crate::prelude::*;
-use crate::{theme, Avatar, Player};
-
-#[derive(Element)]
-pub struct Facepile {
-    players: Vec<Player>,
-}
-
-impl Facepile {
-    pub fn new<P: Iterator<Item = Player>>(players: P) -> Self {
-        Self {
-            players: players.collect(),
-        }
-    }
-
-    fn render<V: 'static>(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
-        let theme = theme(cx);
-        let player_count = self.players.len();
-        let player_list = self.players.iter().enumerate().map(|(ix, player)| {
-            let isnt_last = ix < player_count - 1;
-
-            div()
-                .when(isnt_last, |div| div.neg_mr_1())
-                .child(Avatar::new(player.avatar_src().to_string()))
-        });
-        div().p_1().flex().items_center().children(player_list)
-    }
-}