Add ENV variable to debug zeitwerk with logging and eager loading

It's far easier to debug in dev/test/containers using an ENV variable
so we'll make it so zeitwerk stdout logging and eager loading of all engines
is only done with this flag enabled.

config/application.rb

@@ -164,6 +164,15 @@ class Application < Rails::Application
       Vmdb::Loggers.apply_config(::Settings.log)
     end
 
+    initializer :eager_load_all_the_things, :after => :load_config_initializers do
+      if ENV['DEBUG_MANAGEIQ_ZEITWERK'].present?
+        config.eager_load_paths += config.autoload_paths
+        Vmdb::Plugins.each do |plugin|
+          plugin.config.eager_load_paths += plugin.config.autoload_paths
+        end
+      end
+    end
+
     config.after_initialize do
       Vmdb::Initializer.init
       ActiveRecord::Base.connection_pool.release_connection

config/initializers/zeitwerk.rb

@@ -1,4 +1,9 @@
 if Rails.application.config.autoloader == :zeitwerk && Rails.autoloaders.main
+  if ENV['DEBUG_MANAGEIQ_ZEITWERK'].present?
+    Zeitwerk::Loader.default_logger = method(:puts)
+    Rails.autoloaders.main.logger = Logger.new($stdout)
+  end
+
   # These specific directories are for code organization, not namespacing:
   # TODO: these should be either renamed with good names, the intermediate directory removed
   # and/or both.