Add cold-start follow recommendations (#15945)

app/controllers/admin/follow_recommendations_controller.rb

app/controllers/api/v1/suggestions_controller.rb

app/controllers/api/v2/suggestions_controller.rb

app/javascript/mastodon/actions/suggestions.js

...pt/mastodon/features/compose/components/search_results.js

app/javascript/mastodon/reducers/suggestions.js

app/lib/potential_friendship_tracker.rb

app/models/account.rb

app/models/account_suggestions.rb

app/models/account_summary.rb

app/models/concerns/account_associations.rb

app/models/follow_recommendation.rb

app/models/follow_recommendation_filter.rb

app/models/follow_recommendation_suppression.rb

app/models/form/account_batch.rb

app/policies/follow_recommendation_policy.rb

app/serializers/rest/suggestion_serializer.rb

app/views/admin/follow_recommendations/_account.html.haml

app/views/admin/follow_recommendations/show.html.haml

app/workers/scheduler/follow_recommendations_scheduler.rb