Mainline GPUI2 UI work (#3062)

This PR mainlines the current state of new GPUI2-based UI from the
`gpui2-ui` branch.

Release Notes:

- N/A

---------

Co-authored-by: Nate Butler <iamnbutler@gmail.com>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Marshall Bowers <1486634+maxdeviant@users.noreply.github.com>
Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Nate <nate@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/ui/src/components/context_menu.rs

@@ -0,0 +1,65 @@
+use crate::prelude::*;
+use crate::theme::theme;
+use crate::{
+    v_stack, Label, List, ListEntry, ListItem, ListItemVariant, ListSeparator, ListSubHeader,
+};
+
+#[derive(Clone)]
+pub enum ContextMenuItem {
+    Header(&'static str),
+    Entry(Label),
+    Separator,
+}
+
+impl ContextMenuItem {
+    fn to_list_item(self) -> ListItem {
+        match self {
+            ContextMenuItem::Header(label) => ListSubHeader::new(label).into(),
+            ContextMenuItem::Entry(label) => {
+                ListEntry::new(label).variant(ListItemVariant::Inset).into()
+            }
+            ContextMenuItem::Separator => ListSeparator::new().into(),
+        }
+    }
+    pub fn header(label: &'static str) -> Self {
+        Self::Header(label)
+    }
+    pub fn separator() -> Self {
+        Self::Separator
+    }
+    pub fn entry(label: Label) -> Self {
+        Self::Entry(label)
+    }
+}
+
+#[derive(Element)]
+pub struct ContextMenu {
+    items: Vec<ContextMenuItem>,
+}
+
+impl ContextMenu {
+    pub fn new(items: impl IntoIterator<Item = ContextMenuItem>) -> Self {
+        Self {
+            items: items.into_iter().collect(),
+        }
+    }
+    fn render<V: 'static>(&mut self, view: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        let theme = theme(cx);
+        v_stack()
+            .flex()
+            .fill(theme.lowest.base.default.background)
+            .border()
+            .border_color(theme.lowest.base.default.border)
+            .child(
+                List::new(
+                    self.items
+                        .clone()
+                        .into_iter()
+                        .map(ContextMenuItem::to_list_item)
+                        .collect(),
+                )
+                .set_toggle(ToggleState::Toggled),
+            )
+        //div().p_1().children(self.items.clone())
+    }
+}