Ability to paginate a user's posts

When visiting a user's profile in AdminFE, it only shows the last 20 posts of that user. AdminFE should support some kind of pagination so I can find older posts.

I'm not sure the AdminAPI even supports pagination: https://docs-develop.pleroma.social/backend/API/admin_api/#get-apipleromaadminusersnickname_or_idstatuses

mentioned in issue pleroma#2388 (closed)

mentioned in merge request !196