Mainline GPUI2 UI work (#3079)

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: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Nate <nate@zed.dev>

crates/ui/src/components/tab.rs

@@ -1,7 +1,7 @@
 use crate::prelude::*;
 use crate::{theme, Icon, IconColor, IconElement, Label, LabelColor};
 
-#[derive(Element)]
+#[derive(Element, Clone)]
 pub struct Tab {
     title: String,
     icon: Option<Icon>,