Create an "Experimental feature" setting for the progress storage

[m1r0]

Goal

We need an "experimental feature" setting that enables the new progress and quiz data storage.

This will allow users to test the feature before it's fully ready.

Scope

• Create an "Advanced" tab in Sensei LMS -> Settings.
• In the "Advanced" tab, have an "Experimental Features" section (similar to woo).
• Under the "Experimental Features" section, add a setting that enables the progress storage.