feat: Add support for desired_capacity_type (named desired_size_type) on self-managed node group

[dtscssap]

Description

• sets the desired_capacity_type for the aws_autoscaling_group resource to AWS default value "units"

Motivation and Context

• current implementation succeeds with leaving this attribute undefined which AWS will set to its default "units" on their end, but evidently subsequent runs of Terraform don't see this during a refresh of state

  • if a user goes into the AWS Console and edits the Autoscaling Group (changes nothing, just clicks the Save button), Terraform will suddenly see this attribute when it refreshes state 🤦

  • if this happens, you will have no choice but to destroy the autoscaling group and recreate via the Terraform because without this change there is no way to tell the current module to not try to set the desired_capacity_type = "units" -> null

      # module.eks_al2.module.self_managed_node_group["example"].aws_autoscaling_group.this will be updated in-place
      ~ resource "aws_autoscaling_group" "this" {
          - desired_capacity_type            = "units" -> null
            id                               = "example"
            name                             = "example"
            # (26 unchanged attributes hidden)
    
            # (39 unchanged blocks hidden)
        }
    
    Plan: 0 to add, 1 to change, 0 to destroy.
    
    Do you want to perform these actions?
      Terraform will perform the actions described above.
      Only 'yes' will be accepted to approve.
    
      Enter a value: yes
    
    module.eks_al2.module.self_managed_node_group["example"].aws_autoscaling_group.this: Modifying... [id=<redacted>]
    ╷
    │ Error: updating Auto Scaling Group (example): InvalidParameter: 1 validation error(s) found.
    │ - minimum field size of 1, UpdateAutoScalingGroupInput.DesiredCapacityType.
    │ 
    

Breaking Changes

• no, "units" is the default value

How Has This Been Tested?

• [ X ] I have updated at least one of the examples/* to demonstrate and validate my change(s)
  • I have not as there is nothing to show, this is a value that is being set under the hood
• I have tested and validated these changes using one or more of the provided examples/* projects

• I have executed pre-commit run -a on my pull request

[ftieben]

Please create var.desired_capacity_type and make "units" as a default value

[antonbabenko]

This PR is included in version 20.26.0 🎉

[github-actions]

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