feat(container/serverless): add scaling_option block

[nullabe]

Description

A new ScalingOption object was added to containers. It replace current max_concurrency. The old field should be marked as deprecated while adding the new object.

API Reference: https://www.scaleway.com/en/developers/api/serverless-containers/#path-containers-create-a-new-container

New or Affected Resource(s)

• scaleway_container

Terraform configuration

resource scaleway_container main {
    namespace_id = scaleway_container_namespace.main.id
    deploy = false
    
    scaling_option {
        concurrent_requests_threshold = 15
    }
}

Related issues

• feat(container): implement ScalingOption #2811
• serverless_containers: add custom autoscaling CPU / RAM #2812

Notes for the reviewer(s)

• Using scaling_option terraform configuration to be compliant with the API.
• Acceptance tests from real calls have been created on both resource and data.
• Documentation has been updated.
• An error is thrown if the user setup more than one option (according to API this should not be possible).
• Errors has not been checked with specific tests cases, it may be useful (but I don't know how to do it).