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/copilot_ui/src/copilot_button.rs

@@ -17,7 +17,9 @@ use util::{paths, ResultExt};
 use workspace::{
     create_and_open_local_file,
     item::ItemHandle,
-    ui::{popover_menu, ButtonCommon, Clickable, ContextMenu, Icon, IconButton, IconSize, Tooltip},
+    ui::{
+        popover_menu, ButtonCommon, Clickable, ContextMenu, IconButton, IconName, IconSize, Tooltip,
+    },
     StatusItemView, Toast, Workspace,
 };
 use zed_actions::OpenBrowser;
@@ -51,15 +53,15 @@ impl Render for CopilotButton {
             .unwrap_or_else(|| all_language_settings.copilot_enabled(None, None));
 
         let icon = match status {
-            Status::Error(_) => Icon::CopilotError,
+            Status::Error(_) => IconName::CopilotError,
             Status::Authorized => {
                 if enabled {
-                    Icon::Copilot
+                    IconName::Copilot
                 } else {
-                    Icon::CopilotDisabled
+                    IconName::CopilotDisabled
                 }
             }
-            _ => Icon::CopilotInit,
+            _ => IconName::CopilotInit,
         };
 
         if let Status::Error(e) = status {