Add wiring for UI density (#11260)

Note: You shouldn't use the `unstable.ui_density` setting – it is only
being added for testing and to enable new UI components to be built with
density in mind. Don't expect this to work well, or at all right now.

Adds some of the basic wiring we'll need to start scaling UI elements
throughout the app based on a desired density setting.

Release Notes:

- N/A

crates/workspace/src/status_bar.rs

@@ -37,10 +37,10 @@ impl Render for StatusBar {
         h_flex()
             .w_full()
             .justify_between()
-            .gap_2()
-            .py_0p5()
-            .px_1()
-            .h_8()
+            .gap(Spacing::Large.rems(cx))
+            .py(Spacing::Small.rems(cx))
+            .px(Spacing::Large.rems(cx))
+            // .h_8()
             .bg(cx.theme().colors().status_bar_background)
             .child(self.render_left_tools(cx))
             .child(self.render_right_tools(cx))
@@ -48,16 +48,16 @@ impl Render for StatusBar {
 }
 
 impl StatusBar {
-    fn render_left_tools(&self, _: &mut ViewContext<Self>) -> impl IntoElement {
+    fn render_left_tools(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
         h_flex()
-            .gap_2()
+            .gap(Spacing::Large.rems(cx))
             .overflow_x_hidden()
             .children(self.left_items.iter().map(|item| item.to_any()))
     }
 
-    fn render_right_tools(&self, _: &mut ViewContext<Self>) -> impl IntoElement {
+    fn render_right_tools(&self, cx: &mut ViewContext<Self>) -> impl IntoElement {
         h_flex()
-            .gap_2()
+            .gap(Spacing::Large.rems(cx))
             .children(self.right_items.iter().rev().map(|item| item.to_any()))
     }
 }

crates/workspace/src/toolbar.rs

@@ -104,15 +104,17 @@ impl Render for Toolbar {
         let has_right_items = self.right_items().count() > 0;
 
         v_flex()
-            .p_2()
-            .when(has_left_items || has_right_items, |this| this.gap_2())
+            .p(Spacing::Large.rems(cx))
+            .when(has_left_items || has_right_items, |this| {
+                this.gap(Spacing::Large.rems(cx))
+            })
             .border_b()
             .border_color(cx.theme().colors().border_variant)
             .bg(cx.theme().colors().toolbar_background)
             .child(
                 h_flex()
                     .justify_between()
-                    .gap_2()
+                    .gap(Spacing::Large.rems(cx))
                     .when(has_left_items, |this| {
                         this.child(
                             h_flex()