[Order Details] Rely on needsProcessing property when checking isEligibleForPayment

[iamgabrielma]

Order has a new needsProcessing property since WC 6.6

At the moment, we check if the Order's datePaid == nil to determine that an Order is eligible for payment, which can cause problems when an Order is switched manually between different statuses, as statuses like complete or processing will generate a date.

Related: https://github.com/woocommerce/woocommerce-ios/pull/7277 and https://github.com/woocommerce/woocommerce-ios/issues/7209