Embargoed country redundancy check for provisioning-related callout workers

### Problem

As described in https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/6053+, there are a few methods of preventing operations from embargoed countries or companies currently in CDot.  There are Customer model validations that prevent a sale, pre-transaction.  There is also an "EmbargoChecker" service for specific countries (Russia, Belarus) and products (SM).  In both circumstances, the country field on the Customer model is used.  However as we want to embrace using Contact data for the Zuora Account when a Customer converts to paid, this logic will need to be updated.

Provisioning is handled through a few services that process Zuora callouts: [ZuoraCallbackWorker](https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/fdfe35c10eb1b72120f7732d69b19cece0172180/app/workers/zuora_callback_worker.rb) and [SubscriptionTermStartWorker](https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/26741557a159d7d6c6a5084fe0fe06aa9aba2a3a/app/workers/zuora_callout/subscription_term_start_worker.rb).  These services have [logic to find or create a customer](https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/32cde3637e1a9b987a7dcc8f6354168253ad272f/app/workers/zuora_callout/base_worker.rb#L24) which currently fail ungracefully when the Sold To Contact/Customer is from a Country on the rejection list due to [this validation](https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/32cde3637e1a9b987a7dcc8f6354168253ad272f/app/models/customer.rb#L51).

### Proposal

In this issue, let's add a redundancy check to these Zuora Callback workers that relate to provisioning to verify the country is not one of the Embargoed List (see below).  This check should validate against the country of the Sold To and Bill To Contact.

* Cuba
* Iran
* Democratic People's Republic of Korea
* Sudan
* Syria

This change can be released without the use of a feature flag as it can be applied independently of other changes mentioned in https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/6053#note_1347043834.

Currently callout workers fail at [this step](https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/1bbc5a161bc07335bf46c08b4b2364f3a73c8849/app/workers/zuora_callout/base_worker.rb#L24) where the customer if either created or updated based on callout attributes.

- [Sentry issue](https://sentry.gitlab.net/gitlab/customersgitlabcom/issues/4099448/?query=is%3Aunresolved%20country) for the `SubscriptionTermStartWorker`
- [Sentry issue](https://sentry.gitlab.net/gitlab/customersgitlabcom/issues/4099799/?query=is%3Aunresolved%20country) for the ZuoraCallbackWorker

We should update these workers with code to verify country.  If it's invalid, the worker could log the event as info or warn, then skip processing the remainder of the worker.  

It's worth noticing that the `AuditProvisionService` will make note that the provision was skipped because of an unsupported country [here](https://gitlab.com/gitlab-org/customers-gitlab-com/-/blob/58055f39852434752768d4d7f51cc4d0817871c0/app/services/provisions/audit_provision_service.rb#L56).

Story points: 3.0