Prelaunch: use .ez files when discovering rabbitmq.conf schemas in 3rd party plugins

and not .ex files, which are Elixir source files.

(cherry picked from commit 36ea6f5)

Author: michaelklishin

deps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl

@@ -350,7 +350,7 @@ list_apps1([Dir | Rest], Apps) ->
         {ok, Filenames} ->
             NewApps = [list_to_atom(
                          hd(
-                           string:split(filename:basename(F, ".ex"), "-")))
+                           string:split(filename:basename(F, ".ez"), "-")))
                        || F <- Filenames],
             Apps1 = lists:umerge(Apps, lists:sort(NewApps)),
             list_apps1(Rest, Apps1);