[SG-31495] [Accessibility]: User dropdown doesn't focus when clicked

Created by: gitstart-sourcegraph

Descriptions:

• Remove controlled states support in <Menu /> component
• Remove all openByDefault prop in UserNavItem and MenuNavItem
• Use ref to open menu in stories

Refs:

• SourceGraph Issue
• GitStart ticket

Test plan

Open web app at homepage and Signin, Open the user dropdown by clicking on the icon with your mouse, Press the down arrow key. Confirm that you can navigate properly within the dropdown