Create "Create new" menu in the super sidebar

What does this MR do and why?

This creates the "Create new" menu in the super sidebar.

This also slightly changes that menu's groups' titles by adding the "In" prefix. This particular change also affects the existing menu as we are using the same Ruby helpers to generate the links in both the northstar and legacy navs.

Screenshots or screen recordings

Within the super sidebar

Closed	Open

Current dropdown menu (groups titles change)

How to set up and validate locally

1. Enable the feature flag:

echo "Feature.enable(:super_sidebar_nav)" | rails c

1. Enable the user setting from the user dropdown:
2. The super sidebar should now appear on every page.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #385744 (closed)