Extension deprecation: Remove extension controls from admin interface

Created by: philipp-spiess

Depends on #39523 Fixes #39051 (closed)

This PR removes the extension controls in the admin interface. It depends on experimental flags that will be added in #39523 but I've hard coded the value for now.

Test plan

Before

After

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.