pac: Skip parent code validation for re-auth if no valid config.

Detect absence of parent access code config and do not perform
code validation for re-auth in that case. This will allow Family
Link users to do online sign-in and fetch the config as a part of
that process.
User can get into no config state if sign-in is interrupted
for example by crash or reboot.

Bug: 1161741
Change-Id: I1d20310a9d5626b060136f5b76d755ccf627b536
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2771198
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Li Lin <llin@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#865968}

• ash/child_accounts/parent_access_controller_impl.cc[diff]
• ash/child_accounts/parent_access_controller_impl.h[diff]
• ash/child_accounts/parent_access_controller_impl_unittest.cc[diff]
• ash/login/login_screen_controller.cc[diff]
• ash/login/login_screen_controller.h[diff]
• ash/login/mock_login_screen_client.cc[diff]
• ash/login/mock_login_screen_client.h[diff]
• ash/public/cpp/child_accounts/DIR_METADATA[Added - diff]
• ash/public/cpp/child_accounts/parent_access_controller.h[diff]
• ash/public/cpp/login_screen_client.h[diff]
• chrome/browser/chromeos/child_accounts/parent_access_code/parent_access_service.cc[diff]
• chrome/browser/chromeos/child_accounts/parent_access_code/parent_access_service.h[diff]
• chrome/browser/chromeos/child_accounts/parent_access_code/parent_access_service_browsertest.cc[diff]
• chrome/browser/chromeos/child_accounts/screen_time_controller.cc[diff]
• chrome/browser/chromeos/child_accounts/screen_time_controller.h[diff]
• chrome/browser/ui/ash/login_screen_client.cc[diff]
• chrome/browser/ui/ash/login_screen_client.h[diff]
• tools/metrics/histograms/enums.xml[diff]
• tools/metrics/histograms/histograms_xml/others/histograms.xml[diff]