[RFE] ignore quantity if cluster-autoscaler is installed

[nickvth]

Is your feature request related to a problem? Please describe.

We are using dynamic block for machine_pools so we can't ignore changes on quantity see https://discuss.hashicorp.com/t/use-lifecycle-ignore-changes-on-dynamic-block/48483

Describe the solution you'd like

We like to have a setting to ignore quantity if we use cluster-autoscaler. For example ignore_quantity = true in machine_pools block, for each machine pool, so we can only ignore when worker_role = true ignore only when machine_pool already exists.

Describe alternatives you've considered

There is no alternative.

Additional context