Use atoms as keys in `ActivityPub.fetch_*` functions options

benchmarks/load_testing/fetcher.ex

benchmarks/mix/tasks/pleroma/benchmarks/tags.ex

lib/pleroma/bbs/handler.ex

lib/pleroma/conversation/participation.ex

lib/pleroma/pagination.ex

lib/pleroma/web/activity_pub/activity_pub.ex

lib/pleroma/web/activity_pub/activity_pub_controller.ex

lib/pleroma/web/activity_pub/utils.ex

...pleroma/web/admin_api/controllers/admin_api_controller.ex

lib/pleroma/web/admin_api/controllers/status_controller.ex

lib/pleroma/web/admin_api/views/report_view.ex

lib/pleroma/web/controller_helper.ex

lib/pleroma/web/feed/tag_controller.ex

lib/pleroma/web/feed/user_controller.ex

...leroma/web/mastodon_api/controllers/account_controller.ex

...a/web/mastodon_api/controllers/conversation_controller.ex

...pleroma/web/mastodon_api/controllers/status_controller.ex

...eroma/web/mastodon_api/controllers/timeline_controller.ex

lib/pleroma/web/mastodon_api/views/conversation_view.ex

...pleroma/web/pleroma_api/controllers/account_controller.ex