Split Interactive into Interactive and Toggleable (#2628)

This is a part of the intensity driven theme rewrite. 

It introduces the `toggle` and `interactive` helper functions to build
Toggle<T> and Interactive<T> styles for interactive elements in the
theme.

This PR also removes the `theme_testbench` crate and related actions.

Huge thanks to @osiewicz and @mikayla-maki for pushing this forward 🙏🏽

Release Notes:

- Updated the style of many interactive elements.

crates/workspace/src/dock.rs

@@ -498,7 +498,9 @@ impl View for PanelButtons {
                     Stack::new()
                         .with_child(
                             MouseEventHandler::<Self, _>::new(panel_ix, cx, |state, cx| {
-                                let style = button_style.style_for(state, is_active);
+                                let style = button_style.in_state(is_active);
+
+                                let style = style.style_for(state);
                                 Flex::row()
                                     .with_child(
                                         Svg::new(view.icon_path(cx))

crates/workspace/src/notifications.rs

@@ -291,7 +291,7 @@ pub mod simple_message_notification {
                         )
                         .with_child(
                             MouseEventHandler::<Cancel, _>::new(0, cx, |state, _| {
-                                let style = theme.dismiss_button.style_for(state, false);
+                                let style = theme.dismiss_button.style_for(state);
                                 Svg::new("icons/x_mark_8.svg")
                                     .with_color(style.color)
                                     .constrained()
@@ -323,7 +323,7 @@ pub mod simple_message_notification {
                                 0,
                                 cx,
                                 |state, _| {
-                                    let style = theme.action_message.style_for(state, false);
+                                    let style = theme.action_message.style_for(state);
 
                                     Flex::row()
                                         .with_child(

crates/workspace/src/pane.rs

@@ -1410,7 +1410,7 @@ impl Pane {
     pub fn render_tab_bar_button<F: 'static + Fn(&mut Pane, &mut EventContext<Pane>)>(
         index: usize,
         icon: &'static str,
-        active: bool,
+        is_active: bool,
         tooltip: Option<(String, Option<Box<dyn Action>>)>,
         cx: &mut ViewContext<Pane>,
         on_click: F,
@@ -1420,7 +1420,7 @@ impl Pane {
 
         let mut button = MouseEventHandler::<TabBarButton, _>::new(index, cx, |mouse_state, cx| {
             let theme = &settings::get::<ThemeSettings>(cx).theme.workspace.tab_bar;
-            let style = theme.pane_button.style_for(mouse_state, active);
+            let style = theme.pane_button.in_state(is_active).style_for(mouse_state);
             Svg::new(icon)
                 .with_color(style.color)
                 .constrained()

crates/workspace/src/toolbar.rs

@@ -231,7 +231,7 @@ fn nav_button<A: Action, F: 'static + Fn(&mut Toolbar, &mut ViewContext<Toolbar>
 ) -> AnyElement<Toolbar> {
     MouseEventHandler::<A, _>::new(0, cx, |state, _| {
         let style = if enabled {
-            style.style_for(state, false)
+            style.style_for(state)
         } else {
             style.disabled_style()
         };