Turn on security token PIN for existing user pods

When the security token PIN is requested during the authentication of an
existing user, use the UI implementation that shows it embedded into the
existing user's pod on the Ash Login Screen.

This CL reuses the implementation that was added and enabled for the Ash
Lock Screen in CLs https://crrev.com/c/1730164 and
https://crrev.com/c/1737490.

Bug: 990391
Test: enroll a Chromebook, configure device policies to force-install smart card middleware onto Login Screen, log in using a SAML account that uses smart card authentication, logout, click on the user pod, click "Unlock with the smart card", check that the PIN keyboard appears on it
Change-Id: I7144488f792cc96d4b989827dff92a7f446b97d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1746259
Reviewed-by: Denis Kuznetsov <antrim@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686055}
4 files changed