Mash cleanup: remove more functions from mojom::LoginScreen

TBR=estade@chromium.org, tsepez@chromium.org

(cherry picked from commit 481f244592236367330cb53f4fe5092f378110a5)

Bug: 958206
Change-Id: I66b1924d9ab0d49047a7ee3fe8d1b696b74ed726
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1637865
Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#665171}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1661666
Cr-Commit-Position: refs/branch-heads/3809@{#369}
Cr-Branched-From: d82dec1a818f378c464ba307ddd9c92133eac355-refs/heads/master@{#665002}

• ash/login/login_screen_controller.cc[diff]
• ash/login/login_screen_controller.h[diff]
• ash/login/ui/lock_contents_view.cc[diff]
• ash/login/ui/lock_contents_view.h[diff]
• ash/login/ui/lock_contents_view_unittest.cc[diff]
• ash/login/ui/lock_debug_view.cc[diff]
• ash/login/ui/login_auth_user_view.cc[diff]
• ash/login/ui/login_auth_user_view.h[diff]
• ash/login/ui/login_data_dispatcher.cc[diff]
• ash/login/ui/login_data_dispatcher.h[diff]
• ash/public/cpp/login_screen_model.h[diff]
• ash/public/cpp/login_types.cc[diff]
• ash/public/cpp/login_types.h[diff]
• ash/public/interfaces/login_screen.mojom[diff]
• chrome/browser/chromeos/child_accounts/screen_time_controller.cc[diff]
• chrome/browser/chromeos/child_accounts/screen_time_controller.h[diff]
• chrome/browser/chromeos/login/lock/screen_locker.cc[diff]
• chrome/browser/chromeos/login/lock/screen_locker.h[diff]
• chrome/browser/chromeos/login/lock/screen_locker_browsertest.cc[diff]
• chrome/browser/chromeos/login/user_board_view_mojo.cc[diff]
• chrome/browser/ui/ash/test_login_screen.cc[diff]
• chrome/browser/ui/ash/test_login_screen.h[diff]
• chrome/browser/ui/ash/test_login_screen_model.cc[diff]
• chrome/browser/ui/ash/test_login_screen_model.h[diff]