Use AS::Dependencies interlock with classic autoloader

With zeitwerk, we actually get deadlocks with the use of the interlock.
This change allows us to use the interlock on master when using the classic autoloader and skip the interlock when using zeitwerk.

#22000

lib/extensions/as_dependencies_interlock.rb

@@ -0,0 +1,31 @@
+module AsDependenciesInterlock
+  # The classic autoloader needs the ActiveSupport::Dependencies.interlock
+  # to avoid deadlocks.  With zeitwerk, this actually causes deadlocks so
+  # we only use the interlock with the classic autoloader.
+  def loading(&block)
+    if Rails.application.config.autoloader == :zeitwerk
+      warn_about_zeitwerk_and_interlock
+      yield
+    else
+      super
+    end
+  end
+
+  def permit_concurrent_loads(&block)
+    if Rails.application.config.autoloader == :zeitwerk
+      warn_about_zeitwerk_and_interlock
+      yield
+    else
+      super
+    end
+  end
+
+  def warn_about_zeitwerk_and_interlock
+    @warn_about_zeitwerk_and_interlock ||= begin
+      warn ":zeitwerk is the configured autoloader. This patched file should be removed: #{__FILE__} once support for the classic loader is dropped. Additionally remove all uses of AS::Depedencies.interlock."
+      true
+    end
+  end
+end
+
+ActiveSupport::Dependencies.interlock.singleton_class.prepend(AsDependenciesInterlock)