Add user tracking to the new navigation beta toggle

What does this MR do and why?

This branch adds snowplow user tracking to the "new navigation" alpha/beta toggle.

Screenshots or screen recordings

How to set up and validate locally

1. Set up Snowplow tracking in your local GDK instance
2. Install the Snowplow debugger Chrome extension
3. Ensure the super_sidebar_nav feature flag is enabled.
4. Navigate to your local GDK and sign in
5. Visit any page where the top navigation menu is visible
6. Open the snowplow debugger panel
7. Click on the toggle to enable the "new navigation" alpha/beta preview
8. Observe that an event labeled enable_new_nav_beta or disable_new_nav_beta shows up in the snowplow debugger panel

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.