Wrap the uglifier compressor with harmony support

* Allows es6 code that regular Uglifier doesn't support
* Avoids requiring Uglifier in all rails processes at application startup.
  * Uglifier requires a js runtime such as node
  * JS runtime can continue to be only available in development and for production pre-compilation

This is a better solution than #9244

Note, the original es6 workaround suggested by Uglifier is to use this harmony support:
https://www.github.com/lautis/uglifier/issues/127

lib/manageiq/ui/classic/engine.rb

@@ -37,10 +37,15 @@ class Engine < ::Rails::Engine
         config.assets.paths << root.join('vendor', 'assets', 'stylesheets').to_s
 
         if Rails.env.production? || Rails.env.test?
-          # Workaround rails 7 + es6 syntax in some js causing uglifier errors by running harmony mode
-          # See: https://www.github.com/lautis/uglifier/issues/127
-          require 'uglifier'
-          config.assets.js_compressor = Uglifier.new(:harmony => true)
+          config.assets.configure do |env|
+            # Workaround rails 7 + es6 syntax in some js causing uglifier errors by running harmony mode
+            # See: https://www.github.com/lautis/uglifier/issues/127
+            # Note, we're purposely using our own compressor to avoid requiring uglifier at application boot time
+            # since this require a js runtime such as node.
+            require 'manageiq/ui/classic/js_compressor'
+            env.register_compressor 'application/javascript', :manageiq_ui_classic_js_compressor, ManageIQ::UI::Classic::JsCompressor
+          end
+          config.assets.js_compressor = :manageiq_ui_classic_js_compressor
         end
 
         def self.vmdb_plugin?

lib/manageiq/ui/classic/js_compressor.rb

@@ -0,0 +1,13 @@
+module ManageIQ
+  module UI
+    module Classic
+      class JsCompressor < Sprockets::UglifierCompressor
+        def initialize(options = {})
+          warn "\e[33m** Using #{self.class.name} with Uglifier.new(:harmony => true) from: #{__FILE__}:#{__LINE__}\e[0m"
+          options[:harmony] = true
+          super(options)
+        end
+      end
+    end
+  end
+end