[EKS] [allocation_strategy]: Support on EKS API allocation_strategy.

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**Tell us about your request, What do you want us to build?**

Can be possible on aws_eks_node_group set the setting related to mixed groups and strategies. Checking on [eks API](https://docs.aws.amazon.com/eks/latest/APIReference/API_CreateNodegroup.html#API_CreateNodegroup_SeeAlso) doesn't exist these settings.

```
spot_allocation_strategy
protect_from_scale_in
on_demand_base_capacity
on_demand_percentage_above_base_capacity
```

**Which service(s) is this request for?**

On EKS service.

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

I want to use aws_eks_node_group on terraform and can define mixed groups and the strategy for them, but it´s not possible because the eks API still doesn't support node_groups in these settings.
Check this [issue](https://github.com/hashicorp/terraform-provider-aws/issues/21707#issuecomment-1327798685)

**Are you currently working around this issue?**

How are you currently solving this problem?
You can migrate to use ASG to can define it.

**Additional context**
Anything else we should know?

**Attachments**
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Start with the EKS CreateNodegroup API reference and the aws_eks_node_group context described in the issue. Compare the requested allocation and mixed-group settings with the API, then confirm that the settings are supported by EKS and exposed through the resource; the issue notes ASGs as the current workaround.

Written by the indexing model from the issue text.