Add relationship manager UI (#10268)

app/controllers/relationships_controller.rb

app/controllers/settings/follower_domains_controller.rb

app/helpers/admin/filter_helper.rb

app/javascript/styles/mastodon/tables.scss

app/models/form/account_batch.rb

app/views/relationships/_account.html.haml

app/views/relationships/show.html.haml

app/views/settings/follower_domains/show.html.haml

config/locales/ar.yml

config/locales/ast.yml

config/locales/ca.yml

config/locales/co.yml

config/locales/cs.yml

config/locales/cy.yml

config/locales/da.yml

config/locales/de.yml

config/locales/el.yml

config/locales/en.yml

config/locales/eo.yml

config/locales/es.yml