editor: Context menu aside scrolling (#35985)

Add support for scrolling the contents rendered aside an
`editor::code_context_menus::CodeContextMenu` by introducing the
`scroll_aside` method.

For now this method is only implemented for the
`CodeContextMenu::Completions` variant, which will scroll the aside
contents for an `editor::code_context_menus::CompletionsMenu` element,
as a `ScrollHandle` is added to the aside content that is rendered.

In order to be possible to trigger this via keybindings, a new editor
action is introduced, `ContextMenuScrollAside`, which accepts a number
of lines or pages to scroll the content by.

Lastly, the default keymaps for both MacOS and Linux, as well as for
Zed's vim mode, are updated to ensure that the following keybindings are
supported when a completion menu is open and the completion item's
documentation is rendered aside:

- `ctrl-e`
- `ctrl-y`
- `ctrl-d`
- `ctrl-u`

### Recording


https://github.com/user-attachments/assets/02043763-87ea-46f5-9768-00e907127b69

---

Closes #13194 

Release Notes:

- Added support for scrolling the documentation panel shown alongside
the completion menu in the editor with `cltr-d`, `ctrl-u`, `ctrl-e` and
`ctrl-y`

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: MrSubidubi <finn@zed.dev>

crates/vim/src/normal/scroll.rs

@@ -98,7 +98,7 @@ impl Vim {
         Vim::take_forced_motion(cx);
         self.exit_temporary_normal(window, cx);
         self.update_editor(cx, |_, editor, cx| {
-            scroll_editor(editor, move_cursor, &amount, window, cx)
+            scroll_editor(editor, move_cursor, amount, window, cx)
         });
     }
 }
@@ -106,7 +106,7 @@ impl Vim {
 fn scroll_editor(
     editor: &mut Editor,
     preserve_cursor_position: bool,
-    amount: &ScrollAmount,
+    amount: ScrollAmount,
     window: &mut Window,
     cx: &mut Context<Editor>,
 ) {
@@ -126,7 +126,7 @@ fn scroll_editor(
                 ScrollAmount::Line(amount.lines(visible_line_count) - 1.0)
             }
         }
-        _ => amount.clone(),
+        _ => amount,
     };
 
     editor.scroll_screen(&amount, window, cx);