Use multiple hackney pools

* federation (ap, salmon)
* media (rich media, media proxy)
* upload (uploader proxy)

Each "part" will stop fighting others ones -- a huge federation outbound
could before make the media proxy fail to checkout a connection in time.

splitted media and uploaded media for the good reason than an upload
pool will have all connections to the same host (the uploader upstream).
it also has a longer default retention period for connections.

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -1311,7 +1311,8 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPIController do
                [],
                adapter: [
                  timeout: timeout,
-                 recv_timeout: timeout
+                 recv_timeout: timeout,
+                 pool: :default
                ]
              ),
            {:ok, data} <- Jason.decode(body) do