Add confirmation screen when handling reports (#22375)

* Add confirmation screen on moderation actions

* Add flash notice when a report has been processed

* Refactor tests

* Add tests

config/i18n-tasks.yml

@@ -58,6 +58,8 @@ ignore_unused:
   - 'errors.429'
   - 'admin.accounts.roles.*'
   - 'admin.action_logs.actions.*'
+  - 'admin.reports.summary.action_preambles.*'
+  - 'admin.reports.summary.actions.*'
   - 'admin_mailer.new_appeal.actions.*'
   - 'statuses.attached.*'
   - 'move_handler.carry_{mutes,blocks}_over_text'