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/Cargo.toml

@@ -1,16 +0,0 @@
-[package]
-name = "ui"
-version = "0.1.0"
-edition = "2021"
-publish = false
-
-[dependencies]
-anyhow.workspace = true
-chrono = "0.4"
-gpui2 = { path = "../gpui2" }
-serde.workspace = true
-settings = { path = "../settings" }
-smallvec.workspace = true
-strum = { version = "0.25.0", features = ["derive"] }
-theme = { path = "../theme" }
-rand = "0.8"