Accept partial copilot suggestions (#8682)

Fixes https://github.com/zed-industries/zed/issues/8020
 
This PR adds a new shortcut cmd-right, if a copilot suggestion exists.
The suggestions is accepted word by word.
It emulates the behaviour of VS Code's Github Copilot implementation.


Release Notes:

- Added ability to accept partial copilot suggestions ([8020](https://github.com/zed-industries/zed/issues/8020))

crates/editor/src/element.rs

@@ -338,6 +338,7 @@ impl EditorElement {
         register_action(view, cx, Editor::display_cursor_names);
         register_action(view, cx, Editor::unique_lines_case_insensitive);
         register_action(view, cx, Editor::unique_lines_case_sensitive);
+        register_action(view, cx, Editor::accept_partial_copilot_suggestion);
     }
 
     fn register_key_listeners(