Add refinements to the keymap UI (#33816)

This includes mostly polishing up the keystroke editing modal, and some
other bits like making the keystroke rendering function more composable.

Release Notes:

- Added refinements to the keymap UI design.

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Ben Kunkle <Ben.kunkle@gmail.com>

crates/ui/src/components/keybinding_hint.rs

@@ -216,7 +216,7 @@ impl Component for KeybindingHint {
     fn preview(window: &mut Window, cx: &mut App) -> Option<AnyElement> {
         let enter_fallback = gpui::KeyBinding::new("enter", menu::Confirm, None);
         let enter = KeyBinding::for_action(&menu::Confirm, window, cx)
-            .unwrap_or(KeyBinding::new(enter_fallback, cx));
+            .unwrap_or(KeyBinding::new_from_gpui(enter_fallback, cx));
 
         let bg_color = cx.theme().colors().surface_background;