Restructure ui into just elements and components (#3023)

This PR restructures the `ui` crate into just `elements` and
`components`.

This was already done on the `gpui2-ui` branch, just getting it onto
`main`.

Release Notes:

- N/A

---------

Co-authored-by: Nate Butler <nate@zed.dev>

crates/ui/src/components/project_panel.rs

@@ -0,0 +1,62 @@
+use crate::{
+    input, list, list_section_header, prelude::*, static_project_panel_project_items,
+    static_project_panel_single_items, theme,
+};
+
+use gpui2::{
+    elements::{div, div::ScrollState},
+    style::StyleHelpers,
+    ParentElement, ViewContext,
+};
+use gpui2::{Element, IntoElement};
+use std::marker::PhantomData;
+
+#[derive(Element)]
+pub struct ProjectPanel<V: 'static> {
+    view_type: PhantomData<V>,
+    scroll_state: ScrollState,
+}
+
+pub fn project_panel<V: 'static>(scroll_state: ScrollState) -> ProjectPanel<V> {
+    ProjectPanel {
+        view_type: PhantomData,
+        scroll_state,
+    }
+}
+
+impl<V: 'static> ProjectPanel<V> {
+    fn render(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        let theme = theme(cx);
+
+        div()
+            .w_56()
+            .h_full()
+            .flex()
+            .flex_col()
+            .fill(theme.middle.base.default.background)
+            .child(
+                div()
+                    .w_56()
+                    .flex()
+                    .flex_col()
+                    .overflow_y_scroll(self.scroll_state.clone())
+                    .child(
+                        list(static_project_panel_single_items())
+                            .header(list_section_header("FILES").set_toggle(ToggleState::Toggled))
+                            .empty_message("No files in directory")
+                            .set_toggle(ToggleState::Toggled),
+                    )
+                    .child(
+                        list(static_project_panel_project_items())
+                            .header(list_section_header("PROJECT").set_toggle(ToggleState::Toggled))
+                            .empty_message("No folders in directory")
+                            .set_toggle(ToggleState::Toggled),
+                    ),
+            )
+            .child(
+                input("Find something...")
+                    .value("buffe".to_string())
+                    .state(InteractionState::Focused),
+            )
+    }
+}