ui: Add functions for generating textual representations of key bindings (#15287)

This PR adds some helper functions in the `ui` crate that can be used to
get textural representations of keystrokes or key bindings.

Release Notes:

- N/A

crates/quick_action_bar/src/quick_action_bar.rs

@@ -27,7 +27,6 @@ pub struct QuickActionBar {
     _inlay_hints_enabled_subscription: Option<Subscription>,
     active_item: Option<Box<dyn ItemHandle>>,
     buffer_search_bar: View<BufferSearchBar>,
-    platform_style: PlatformStyle,
     repl_menu: Option<View<ContextMenu>>,
     show: bool,
     toggle_selections_menu: Option<View<ContextMenu>>,
@@ -45,7 +44,6 @@ impl QuickActionBar {
             _inlay_hints_enabled_subscription: None,
             active_item: None,
             buffer_search_bar,
-            platform_style: PlatformStyle::platform(),
             repl_menu: None,
             show: true,
             toggle_selections_menu: None,