Add qpid_proton stubs for macs so we can run zeitwek:check

Before this, macs had to prevent zeitwerk from testing eager loading
the caller file expecting the Qpid constant to be known.

Now, we can run it:
DEBUG_MANAGEIQ_ZEITWERK=true bin/rails zeitwerk:check --trace

config/initializers/zeitwerk.rb

@@ -10,10 +10,4 @@
   Rails.autoloaders.main.collapse(Rails.root.join("lib/manageiq/reporting/charting"))
   Rails.autoloaders.main.collapse(Rails.root.join("lib/ansible/runner/credential"))
   Rails.autoloaders.main.collapse(Rails.root.join("lib/pdf_generator"))
-
-  # requires qpid, which is an optional dependency because LOL mac
-  if RUBY_PLATFORM.include?("darwin")
-    message_handler_path = Pathname.new(Vmdb::Plugins.paths[ManageIQ::Providers::Nuage::Engine]).join("app/models/manageiq/providers/nuage/network_manager/event_catcher/messaging_handler.rb")
-    Rails.autoloaders.main.ignore(message_handler_path)
-  end
 end

lib/qpid/proton/container.rb

@@ -0,0 +1,9 @@
+# Fake qpid_proton stub so zeitwerk can autoload on platforms that can't build the gem, such as macos.
+if RUBY_PLATFORM.include?("darwin")
+  module Qpid
+    module Proton
+      class Container
+      end
+    end
+  end
+end

lib/qpid/proton/messaging_handler.rb

@@ -0,0 +1,9 @@
+# Fake qpid_proton stub so zeitwerk can autoload on platforms that can't build the gem, such as macos.
+if RUBY_PLATFORM.include?("darwin")
+  module Qpid
+    module Proton
+      class MessagingHandler
+      end
+    end
+  end
+end