Streamer refactoring

.gitignore

config/config.exs

lib/pleroma/activity/ir/topics.ex

lib/pleroma/application.ex

lib/pleroma/notification.ex

lib/pleroma/web/activity_pub/activity_pub.ex

lib/pleroma/web/mastodon_api/websocket_handler.ex

lib/pleroma/web/streamer/ping.ex

lib/pleroma/web/streamer/state.ex

lib/pleroma/web/streamer/streamer.ex

lib/pleroma/web/streamer/streamer_socket.ex

lib/pleroma/web/streamer/supervisor.ex

lib/pleroma/web/streamer/worker.ex

lib/pleroma/web/views/streamer_view.ex

mix.exs

mix.lock

test/activity/ir/topics_test.exs

test/integration/mastodon_websocket_test.exs

test/notification_test.exs

test/support/conn_case.ex