Introduce new stale status to Subscription Contracts

As of API version 2023-07, you can use the new Subscription Contract stale status to express a contract that has been marked as stale due to inactivity.

We're deprecating the SubscriptionDraftErrorCode STALE_CONTRACT and replace it by CONCURRENT_CONTRACT_UPDATE for a better description of the error.

We're introducing the new error code CONTRACT_STALE_STATUS to SubscriptionBillingCycleErrorCode and SubscriptionDraftErrorCode to indicate whenever we attempt to update or bill a contract that hasn't been used for 1 year.