feat: add job to remove stale contacts and contact_inboxes (#11186)

- Add a job to remove stale contacts and contact_inboxes across all accounts

Stale anonymous contact is defined as 
- have no identification (email, phone_number, and identifier are NULL)
- have no conversations
- are older than 30 days

---------

Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

config/schedule.yml

@@ -32,3 +32,10 @@ remove_stale_redis_keys_job.rb:
   cron: '30 22 * * *'
   class: 'Internal::RemoveStaleRedisKeysJob'
   queue: scheduled_jobs
+
+# executed daily at 2230 UTC
+# which is our lowest traffic time
+# process_stale_contacts_job:
+#   cron: '30 22 * * *'
+#   class: 'Internal::ProcessStaleContactsJob'
+#   queue: scheduled_jobs