Add some require calls for newer code (#327)

Author: cretz

temporalio/lib/temporalio/internal/worker/workflow_instance/externally_immutable_hash.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'delegate'
+
 module Temporalio
   module Internal
     module Worker

temporalio/lib/temporalio/workflow.rb

@@ -2,6 +2,7 @@
 
 require 'random/formatter'
 require 'temporalio/error'
+require 'temporalio/internal/worker/workflow_instance'
 require 'temporalio/priority'
 require 'temporalio/workflow/activity_cancellation_type'
 require 'temporalio/workflow/child_workflow_cancellation_type'