Participation panel revamp and fixes

Apollo is a pain in the ass with pagination & filters, so this removes
the tabs system and uses a <select> to filter instead

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

test/federation/activity_pub/transmogrifier_test.exs

@@ -1365,8 +1365,7 @@ defmodule Mobilizon.Federation.ActivityPub.TransmogrifierTest do
       assert event.id
              |> Events.list_participants_for_event()
              |> Map.get(:elements)
-             |> Enum.map(& &1.id) ==
-               []
+             |> Enum.map(& &1.role) == [:rejected]
     end
   end