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

We need to tell Rails autoloaders to ignore them on other platforms
because they won't define the expected constants.

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

@@ -11,9 +11,10 @@
   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)
+  # These stub classes are only for macos to workaround qpid_proton not being installable on mac.
+  # These stubs won't define constants elsewhere, so we need to tell zeitwerk to ignore them.
+  unless RUBY_PLATFORM.include?("darwin")
+    Rails.autoloaders.main.ignore(Rails.root.join("lib/qpid/proton/container.rb"))
+    Rails.autoloaders.main.ignore(Rails.root.join("lib/qpid/proton/messaging_handler.rb"))
   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