Hide the mouse when the user is typing in the editor (#25040)

Closes https://github.com/zed-industries/zed/issues/4461

This PR improves the coding experience by hiding the mouse while the
user is typing so it does not accidentally get in their way, making it
challenging to ready characters in the editor.

Release Notes:

- The following PR hides the cursor when the user is typing by adding a
new cursor style called `None`.
- Assuming the user does not move the mouse, it will stay hidden until
it is moved again.


https://github.com/user-attachments/assets/6ba9f2ee-b9f3-4595-81e4-e9d986da4a39

---------

Co-authored-by: Agus <agus@zed.dev>
Co-authored-by: Peter Tripp <peter@zed.dev>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/editor/src/element.rs

@@ -848,6 +848,7 @@ impl EditorElement {
         let modifiers = event.modifiers;
         let gutter_hovered = gutter_hitbox.is_hovered(window);
         editor.set_gutter_hovered(gutter_hovered, cx);
+        editor.mouse_cursor_hidden = false;
 
         // Don't trigger hover popover if mouse is hovering over context menu
         if text_hitbox.is_hovered(window) {
@@ -4813,9 +4814,10 @@ impl EditorElement {
                 bounds: layout.position_map.text_hitbox.bounds,
             }),
             |window| {
-                let cursor_style = if self
-                    .editor
-                    .read(cx)
+                let editor = self.editor.read(cx);
+                let cursor_style = if editor.mouse_cursor_hidden {
+                    CursorStyle::None
+                } else if editor
                     .hovered_link_state
                     .as_ref()
                     .is_some_and(|hovered_link_state| !hovered_link_state.links.is_empty())
@@ -6815,6 +6817,7 @@ impl Element for EditorElement {
                         },
                         false,
                     );
+
                     // Offset the content_bounds from the text_bounds by the gutter margin (which
                     // is roughly half a character wide) to make hit testing work more like how we want.
                     let content_origin =