Add UI setting components (#13550)

Adds some of the UI components to allow us to visually render settings.

These are UI only and are not functional yet (@maxdeviant will be
working on these when he is back.)

You can see some examples by running `script/storybook setting`.

![CleanShot 2024-06-26 at 12 38
37@2x](https://github.com/zed-industries/zed/assets/1714999/b5e6434d-3bc5-4fcd-9c0a-d280950cbef2)

Release Notes:

- N/A

crates/ui/src/components/dropdown_menu.rs

@@ -0,0 +1,85 @@
+use crate::prelude::*;
+
+/// !!don't use this yet – it's not functional!!
+///
+/// pub crate until this is functional
+///
+/// just a placeholder for now for filling out the settings menu stories.
+#[derive(Debug, Clone, IntoElement)]
+pub(crate) struct DropdownMenu {
+    pub id: ElementId,
+    current_item: Option<SharedString>,
+    // items: Vec<SharedString>,
+    full_width: bool,
+    disabled: bool,
+}
+
+impl DropdownMenu {
+    pub fn new(id: impl Into<ElementId>, _cx: &WindowContext) -> Self {
+        Self {
+            id: id.into(),
+            current_item: None,
+            // items: Vec::new(),
+            full_width: false,
+            disabled: false,
+        }
+    }
+
+    pub fn current_item(mut self, current_item: Option<SharedString>) -> Self {
+        self.current_item = current_item;
+        self
+    }
+
+    pub fn full_width(mut self, full_width: bool) -> Self {
+        self.full_width = full_width;
+        self
+    }
+
+    pub fn disabled(mut self, disabled: bool) -> Self {
+        self.disabled = disabled;
+        self
+    }
+}
+
+impl RenderOnce for DropdownMenu {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
+        let disabled = self.disabled;
+
+        h_flex()
+            .id(self.id)
+            .justify_between()
+            .rounded_md()
+            .bg(cx.theme().colors().editor_background)
+            .pl_2()
+            .pr_1p5()
+            .py_0p5()
+            .gap_2()
+            .min_w_20()
+            .when_else(
+                self.full_width,
+                |full_width| full_width.w_full(),
+                |auto_width| auto_width.flex_none().w_auto(),
+            )
+            .when_else(
+                disabled,
+                |disabled| disabled.cursor_not_allowed(),
+                |enabled| enabled.cursor_pointer(),
+            )
+            .child(
+                Label::new(self.current_item.unwrap_or("".into())).color(if disabled {
+                    Color::Disabled
+                } else {
+                    Color::Default
+                }),
+            )
+            .child(
+                Icon::new(IconName::ChevronUpDown)
+                    .size(IconSize::XSmall)
+                    .color(if disabled {
+                        Color::Disabled
+                    } else {
+                        Color::Muted
+                    }),
+            )
+    }
+}