Improve class comment for Drupal\Core\Menu\MenuLinkTreeElement

Problem/Motivation

The class comment for Drupal\Core\Menu::MenuLinkTreeElement() includes these lines:

/**
 * Provides a value object to model an element in a menu link tree.
 *
 * \Drupal\Core\Menu\MenuLinkTreeElement objects represent a menu link's data.
 * Objects of this class provide complimentary data: the placement in a tree.
...
*/

The class that "represent a menu link's data" should be something other than "this class".

Also, the doc block uses "complimentary" when it means "complementary": in the quoted snippet and again a few lines later.

Proposed resolution

1. Replace MenuLinkTreeElement with MenuLinkInterface
2. Replace "complimentary" with "complementary" (twice).

Remaining tasks

User interface changes

None

API changes

None

Data model changes

None

Release notes snippet

N/A