Start private space setup when there is no private space set

This change handles as below based on if private space already exists on device:
1. If PS doesn't exist then start the setup flow which shows a PS education screen. On setup button creates the private space.
2. If PS already exists on device then display PS settings page.

Bug: 299069146
Test: atest PrivateSpaceSettingsAuthenticatorTest
Change-Id: I46bdbaeb0210fd5b41a426f852e3f455b62c1c29