Hard coded region references remain in installer

This is a clone of issue OCPBUGS-15222. The following is the description of the original issue:
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This is a clone of issue OCPBUGS-9435. The following is the description of the original issue:
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PRs were previously merged to add SC2S support via AWS SDK here:

• https://github.com/openshift/installer/pull/5710
• https://github.com/openshift/installer/pull/5597
• https://github.com/openshift/cluster-ingress-operator/pull/703

However, further updates to add support for SC2S region (us-isob-east-1) and new TC2S region (us-iso-west-1) are still required.

There are still hard coded references to the old regions in the follow locations.

• https://github.com/openshift/installer/blob/2aa8651d244dc3f6342b39f818e2f4c87ac0a623/pkg/types/aws/validation/machinepool.go#L98
• https://github.com/openshift/installer/blob/2aa8651d244dc3f6342b39f818e2f4c87ac0a623/data/data/aws/cluster/route53/base.tf#L8