[Devices management] Add a feature flag and empty screen for future new layout

[mnaturel]

Your use case

What would you like to do?

Adding a feature flag to enable access to the new layout for devices management.

Why would you like to do it?

When developing the new layout, we need a way to enable it along with the current layout.

How would you like to achieve it?

Adding a new feature flag and a new entry in settings.

Have you considered any alternatives?

No response

Additional context

No response

Are you willing to provide a PR?

Yes