Refactor ParentAccessUI to general UI for PIN requests.

The new UI is used both for parent access and by smartcard login.
Several options were added to accommodate the second use case.
All parent access specific logic moved into ParentAccessController, which is
now the single point of access to the UI widget for parent access.

Bug: 1001288
Change-Id: Iee728bb5ae77d387ae999741101e356602618d6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2003169
Commit-Queue: Fabian Sommer <fabiansommer@chromium.org>
Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#740603}

• ash/BUILD.gn[diff]
• ash/login/login_screen_controller.cc[diff]
• ash/login/login_screen_controller.h[diff]
• ash/login/parent_access_controller.cc[Added - diff]
• ash/login/parent_access_controller.h[Added - diff]
• ash/login/parent_access_controller_unittest.cc[Added - diff]
• ash/login/ui/lock_contents_view.cc[diff]
• ash/login/ui/lock_contents_view_unittest.cc[diff]
• ash/login/ui/parent_access_view.cc[diff]
• ash/login/ui/parent_access_view.h[diff]
• ash/login/ui/parent_access_view_unittest.cc[diff]
• ash/login/ui/parent_access_widget.cc[diff]
• ash/login/ui/parent_access_widget.h[diff]
• ash/public/cpp/login_screen.h[diff]
• ash/shell.cc[diff]
• ash/shell.h[diff]
• chrome/browser/ui/ash/test_login_screen.cc[diff]
• chrome/browser/ui/ash/test_login_screen.h[diff]
• chrome/browser/ui/webui/chromeos/set_time_ui.cc[diff]
• chrome/browser/ui/webui/settings/chromeos/date_time_handler.cc[diff]