[PLAN] Implement Drawer

Problem/Motivation

We've decided on a drawer design for the navigation menu. This issue will serve as the Epic-level ticket for the work to implement these designs.

Proposed resolution

Note: This designs show also part of the explorations happening around the admin UI layout redesign and are not part neither from this issue nor the Navigation module.

Remaining tasks

• #3436130: Ensure keyboard navigation works with the drawer
• #3436129: Ensure the drawer works in RTL

Done

• #3427659: Implement drawer functionality
• #3427657: Implement the new designs to the drawer
• #3437401: Drawer closes when moving from the opening item to "popover"
• #3437395: The caret from the 1st menu item shouldn't turn when the drawer opens
• #3436729: Drawer: the text appears below the menu links during the animation
• #3436873: Expanding popover accordions prevent other popovers from appearing
• #3437375: There should be only one submenu expanded in the drawer at a time

User interface changes

The sub-menus interaction will change radically from flyouts to a drawer pattern.