Fix Sidekiq warnings about JSON serialization (#17381)

* Fix Sidekiq warnings about JSON serialization

This occurs on every symbol argument we pass, and every symbol key in hashes,
because Sidekiq expects strings instead.

See https://github.com/mperham/sidekiq/pull/5071

We do not need to change how workers parse their arguments because this has
not changed and we were already converting to symbols adequately or using
`with_indifferent_access`.

* Set Sidekiq to raise on unsafe arguments in test mode

In order to more easily catch issues that would produce warnings in production
code.

config/environments/test.rb

@@ -70,3 +70,6 @@ if ENV['PAM_ENABLED'] == 'true'
       env: { email: 'pam@example.com' }
     }
 end
+
+# Catch serialization warnings early
+Sidekiq.strict_args!