ui2: Reorganize components (#3228)

This PR reorganizes the components in the `ui2` crate.

The distinction between "elements" and "components" is now gone, with
all of the reusable components living under `components/`.

The components that we built while prototyping but will eventually live
in other crates currently reside in the `to_extract/` module.

Release Notes:

- N/A

crates/ui2/src/components/project_panel.rs

@@ -1,77 +0,0 @@
-use crate::prelude::*;
-use crate::{
-    static_project_panel_project_items, static_project_panel_single_items, Input, List, ListHeader,
-};
-
-#[derive(Component)]
-pub struct ProjectPanel {
-    id: ElementId,
-}
-
-impl ProjectPanel {
-    pub fn new(id: impl Into<ElementId>) -> Self {
-        Self { id: id.into() }
-    }
-
-    fn render<V: 'static>(self, _view: &mut V, cx: &mut ViewContext<V>) -> impl Component<V> {
-        div()
-            .id(self.id.clone())
-            .flex()
-            .flex_col()
-            .w_full()
-            .h_full()
-            .bg(cx.theme().colors().surface)
-            .child(
-                div()
-                    .id("project-panel-contents")
-                    .w_full()
-                    .flex()
-                    .flex_col()
-                    .overflow_y_scroll()
-                    .child(
-                        List::new(static_project_panel_single_items())
-                            .header(ListHeader::new("FILES").toggle(ToggleState::Toggled))
-                            .empty_message("No files in directory")
-                            .toggle(ToggleState::Toggled),
-                    )
-                    .child(
-                        List::new(static_project_panel_project_items())
-                            .header(ListHeader::new("PROJECT").toggle(ToggleState::Toggled))
-                            .empty_message("No folders in directory")
-                            .toggle(ToggleState::Toggled),
-                    ),
-            )
-            .child(
-                Input::new("Find something...")
-                    .value("buffe".to_string())
-                    .state(InteractionState::Focused),
-            )
-    }
-}
-
-use gpui2::ElementId;
-#[cfg(feature = "stories")]
-pub use stories::*;
-
-#[cfg(feature = "stories")]
-mod stories {
-    use super::*;
-    use crate::{Panel, Story};
-    use gpui2::{Div, Render};
-
-    pub struct ProjectPanelStory;
-
-    impl Render for ProjectPanelStory {
-        type Element = Div<Self>;
-
-        fn render(&mut self, cx: &mut ViewContext<Self>) -> Self::Element {
-            Story::container(cx)
-                .child(Story::title_for::<_, ProjectPanel>(cx))
-                .child(Story::label(cx, "Default"))
-                .child(
-                    Panel::new("project-panel-outer", cx)
-                        .child(ProjectPanel::new("project-panel-inner")),
-                )
-        }
-    }
-}