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/Cargo.toml

@@ -6,7 +6,10 @@ 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" }