Rename IconElement to just Icon (#3974)

This PR renames the `IconElement` component to just `Icon`.

This better matches the rest of our components, as `IconElement` was the
only one using this naming convention.

The `Icon` enum has been renamed to `IconName` to free up the name.

I was trying to come up with a way that would allow rendering an
`Icon::Zed` directly (and thus make the `IconElement` a hidden part of
the API), but I couldn't come up with a way to do this cleanly.

Release Notes:

- N/A

crates/terminal_view/src/terminal_panel.rs

@@ -19,7 +19,7 @@ use workspace::{
     dock::{DockPosition, Panel, PanelEvent},
     item::Item,
     pane,
-    ui::Icon,
+    ui::IconName,
     DraggedTab, Pane, Workspace,
 };
 
@@ -71,7 +71,7 @@ impl TerminalPanel {
                 h_stack()
                     .gap_2()
                     .child(
-                        IconButton::new("plus", Icon::Plus)
+                        IconButton::new("plus", IconName::Plus)
                             .icon_size(IconSize::Small)
                             .on_click(move |_, cx| {
                                 terminal_panel
@@ -82,10 +82,10 @@ impl TerminalPanel {
                     )
                     .child({
                         let zoomed = pane.is_zoomed();
-                        IconButton::new("toggle_zoom", Icon::Maximize)
+                        IconButton::new("toggle_zoom", IconName::Maximize)
                             .icon_size(IconSize::Small)
                             .selected(zoomed)
-                            .selected_icon(Icon::Minimize)
+                            .selected_icon(IconName::Minimize)
                             .on_click(cx.listener(|pane, _, cx| {
                                 pane.toggle_zoom(&workspace::ToggleZoom, cx);
                             }))
@@ -477,8 +477,8 @@ impl Panel for TerminalPanel {
         "TerminalPanel"
     }
 
-    fn icon(&self, _cx: &WindowContext) -> Option<Icon> {
-        Some(Icon::Terminal)
+    fn icon(&self, _cx: &WindowContext) -> Option<IconName> {
+        Some(IconName::Terminal)
     }
 
     fn icon_tooltip(&self, _cx: &WindowContext) -> Option<&'static str> {

crates/terminal_view/src/terminal_view.rs

@@ -20,7 +20,7 @@ use terminal::{
     Clear, Copy, Event, MaybeNavigationTarget, Paste, ShowCharacterPalette, Terminal,
 };
 use terminal_element::TerminalElement;
-use ui::{h_stack, prelude::*, ContextMenu, Icon, IconElement, Label};
+use ui::{h_stack, prelude::*, ContextMenu, Icon, IconName, Label};
 use util::{paths::PathLikeWithPosition, ResultExt};
 use workspace::{
     item::{BreadcrumbText, Item, ItemEvent},
@@ -690,7 +690,7 @@ impl Item for TerminalView {
         let title = self.terminal().read(cx).title(true);
         h_stack()
             .gap_2()
-            .child(IconElement::new(Icon::Terminal))
+            .child(Icon::new(IconName::Terminal))
             .child(Label::new(title).color(if selected {
                 Color::Default
             } else {