Remove shell_test_api.test-mojom

Instead, this CL exposes the existing ShellTestApi as
ash/public/cpp/test/shell_test_api.h.

Bug: 958216
Test: trybot
Change-Id: I12aaa0aeccc13dbf65dbf90cdd0671d8276eae20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610573
Commit-Queue: Jun Mukai <mukai@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659584}

• ash/BUILD.gn[diff]
• ash/accelerators/accelerator_controller_unittest.cc[diff]
• ash/app_list/app_list_presenter_delegate_unittest.cc[diff]
• ash/display/screen_position_controller_unittest.cc[diff]
• ash/mojo_test_interface_factory.cc[diff]
• ash/public/cpp/test/shell_test_api.h[Added - diff]
• ash/public/cpp/test_manifest.cc[diff]
• ash/public/interfaces/BUILD.gn[diff]
• ash/public/interfaces/shell_test_api.test-mojom[Deleted - diff]
• ash/shelf/shelf_layout_manager_unittest.cc[diff]
• ash/shelf/shelf_view_unittest.cc[diff]
• ash/shell_test_api.cc[diff]
• ash/shell_test_api.h[Deleted - diff]
• ash/shell_unittest.cc[diff]
• ash/system/message_center/inactive_user_notification_blocker_unittest.cc[diff]
• ash/system/palette/palette_tray_unittest.cc[diff]
• ash/system/palette/tools/create_note_unittest.cc[diff]
• ash/system/palette/tools/metalayer_unittest.cc[diff]
• ash/system/palette/tools/screenshot_unittest.cc[diff]
• ash/system/power/power_button_test_base.cc[diff]
• ash/system/power/power_prefs_unittest.cc[diff]
• ash/wallpaper/wallpaper_controller_unittest.cc[diff]
• ash/wm/cursor_manager_test_api.cc[diff]
• ash/wm/system_gesture_event_filter_unittest.cc[diff]
• ash/wm/tablet_mode/tablet_mode_window_manager_unittest.cc[diff]
• ash/wm/workspace/multi_window_resize_controller_unittest.cc[diff]
• ash/wm/workspace/workspace_layout_manager_unittest.cc[diff]
• ash/wm/workspace_controller_unittest.cc[diff]
• chrome/browser/BUILD.gn[diff]
• chrome/browser/chromeos/file_manager/file_manager_browsertest_base.cc[diff]
• chrome/browser/ui/ash/accelerator_commands_browsertest.cc[diff]
• chrome/browser/ui/ash/ash_test_util.cc[Deleted - diff]
• chrome/browser/ui/ash/ash_test_util.h[Deleted - diff]
• chrome/browser/ui/ash/drag_to_overview_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/launcher_animations_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/launcher_drag_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/overview_animations_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/overview_window_drag_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/screen_rotation_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/split_view_interactive_uitest.cc[diff]
• chrome/browser/ui/ash/tablet_mode_client_test_util.cc[diff]
• chrome/browser/ui/ash/tablet_mode_transition_interactive_uitest.cc[diff]
• chrome/browser/ui/views/frame/browser_non_client_frame_view_ash_browsertest.cc[diff]
• chrome/browser/ui/views/frame/immersive_mode_controller_ash_browsertest.cc[diff]
• chrome/browser/ui/views/select_file_dialog_extension_browsertest.cc[diff]
• chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc[diff]
• chrome/browser/ui/webui/chromeos/system_web_dialog_browsertest.cc[diff]
• components/exo/client_controlled_shell_surface_unittest.cc[diff]
• components/exo/shell_surface_unittest.cc[diff]