Render context error on wehook call

PaymentOrderUpdater has its origins in #3011667: Saving the order before its payment in PaymentGateway::onReturn() can cause data loss → . It has been converted into a destructable service in #3085813: Consider moving from Kernel::TERMINATE event to DestructableInterface implementation → . A similar issue has been reported in #3124179: Render context is empty after IPN payment → . Another backtrace referring to the same code location here #3158347: PaymentOrderUpdater destruct called after migration → (related to migrate, though).

My hunch is that something renders a link, an email or some other piece of markup in an event subscriber. That results in a cache metadata leak while the webhook is processing. In order to prevent cache metadata leaking, we might want to wrap the webhook logic into a render context and throw away the results.

@Berdir or @Primsi: would you mind taking a look at the MR?