Add "clean up policy" to corpus management

Problem to solve

Provide an easy way for users to set up a cleanup policy so that it savs time.

Proposal

Design figma:https://www.figma.com/file/eSIeuIPKFwEDs4X9ky2O5E/Corpus-Registry?node-id=661%3A1598

• By default, the policy is off
• User can turn it on after the user turns policy on, a policy summary is showing on the top bar
• When a user turns the policy one we tell the user how many current files matches the policy, which means, we will delete that corpus when user save the policy

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