Factor out LabelLike to share common label styles (#3510)

This PR factors out a new `LabelLike` component to share common styles
between the `Label` and `HighlightedLabel` components.

Release Notes:

- N/A

crates/copilot2/src/sign_in.rs

@@ -5,7 +5,7 @@ use gpui::{
     WindowBounds, WindowHandle, WindowKind, WindowOptions,
 };
 use theme::ActiveTheme;
-use ui::{h_stack, v_stack, Button, Clickable, Color, Icon, IconElement, Label};
+use ui::{prelude::*, Button, Icon, IconElement, Label};
 
 const COPILOT_SIGN_UP_URL: &'static str = "https://github.com/features/copilot";