Introduce access token fabricators (#4401)

...ontrollers/api/v1/accounts/credentials_controller_spec.rb

...lers/api/v1/accounts/follower_accounts_controller_spec.rb

...ers/api/v1/accounts/following_accounts_controller_spec.rb

...trollers/api/v1/accounts/relationships_controller_spec.rb

spec/controllers/api/v1/accounts/search_controller_spec.rb

spec/controllers/api/v1/accounts/statuses_controller_spec.rb

spec/controllers/api/v1/accounts_controller_spec.rb

spec/controllers/api/v1/blocks_controller_spec.rb

spec/controllers/api/v1/domain_blocks_controller_spec.rb

spec/controllers/api/v1/favourites_controller_spec.rb

spec/controllers/api/v1/follow_requests_controller_spec.rb

spec/controllers/api/v1/follows_controller_spec.rb

spec/controllers/api/v1/instances_controller_spec.rb

spec/controllers/api/v1/media_controller_spec.rb

spec/controllers/api/v1/mutes_controller_spec.rb

spec/controllers/api/v1/notifications_controller_spec.rb

spec/controllers/api/v1/reports_controller_spec.rb

spec/controllers/api/v1/search_controller_spec.rb

...api/v1/statuses/favourited_by_accounts_controller_spec.rb

...controllers/api/v1/statuses/favourites_controller_spec.rb