Set instance_type in AWS Launch Template instead of Managed Node Group

[sidewinder12s]

Is your request related to a problem? Please describe.

You cannot modify instance types on managed node groups if you are not using a provided AWS Launch Template. It appears we just need to move the instance_type spec from the MNG to the launch template.

Describe the solution you'd like.

Set the instance_types through Launch template instead of on the managed_node_group config.

Describe alternatives you've considered.

The alternative is to require users to create new MNGs and manually migrate their workloads when they must change them.

Additional context

It appears the main drawback of this is that you cannot specify multiple instance types when setting instance_type through the launch template. That may be undesirable for some users, though I don't think it's generally recommended to have multiple instance sizes in MNGs (or self-managed-node-groups) since then the Autoscaler will not know what size instance it is going to launch.

aws/containers-roadmap#746
aws/containers-roadmap#585

[sidewinder12s]

Before I look at implementing this, does anyone have major objections to changing the instance specification behavior?

@bryantbiggs Was there a reason you left the instance_type variable commented out in this module?

ee9f0c6#diff-4402c3de90b812296b76c12945524bfde8723038f31d2db203eb2b9294f72df8R45

[bryantbiggs]

This is not a change that we'll support here

[github-actions]

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