Nav menu item controls are not (auto-)focusable

[westonruter]

When attempting to access the Customizer with a nav_menu_item control autofocused, using a URL such as:

​http://src.wordpress-develop.dev/wp-admin/customize.php?autofocus[control]=nav_menu_item[4953]

The result is that the Customizer does not focus on that control when it loads. Instead, when attempting to click through to the nav menu item there is an additional regression where you have to click the menu section twice to open it.

The issue with focus on the nav menu item control was addressed previously for Widgets in #33258. The same fix is needed for nav menu items.

[westonruter]

In 35584:

Customize: Fix focus and autofocus on nav_menu_item controls.

Embed the nav_menu_item control not only when the contained nav_menu section expands, but also if the control was autofocused (via the autofocus[control] query param). Also applies change from [33596] to work-around a broken :focusable selector in jQuery UI.

See #33258.
Fixes #34629.