feat!: EKS Node Pool Subnets to use Single AZ by Default

[jarpat]

Changes

In order to line up with the recommendations from the SAS Viya Platform Operations documentation we are updating the code base so that when EKS node groups are created they will be placed in a single-AZ rather than spanning over multiple-AZs. This feature is controlled by the new variable enable_multi_zone which by default will be set to false, resulting in the node groups being a single subnet in a single-az.

This is considered a breaking change single since users who initially created their infrastructure with viya4-iac-aws:7.2.1 or earlier, and want to use the new version to make adjustments to their infrastructure will now have their node groups moved to a single-az. If they have a stopped Viya deployment they were planning on starting after the infrastructure updates, they will most likely run in SAS Viya pod instability as they try to get it back online. Our recommendation for those users is to set enable_multi_zone to true when they run apply again to keep their node groups in a multi-az configuration so that the Viya pods are unaffected. Alternatively if the user wants to move over to a single-az configuration from their previous multi-az deployment following the SAS Viya Platform Operation backup and restore documentation is recommended.

Relevant SAS Viya Platform documentation for AWS Cluster Requirements:
https://documentation.sas.com/?cdcId=itopscdc&cdcVersion=default&docsetId=itopssr&docsetTarget=n098rczq46ffjfn1xbgfzahytnmx.htm#p0vx68bmb3fs88n12d73wwxpsnhu

Tests

Put tests in comment for better formatting:
#234 (comment)

[jarpat]

Tests

Tests move to comment for better formatting

Scenario	Provider	Summary	From	To	K8s Version	enable_multi_zone	Order	Cadence	Notes
1	AWS	Single-AZ OOTB	viya4-iac-aws: PR viya4-deployment: 6.12.0	N/A	v1.26.7-eks-2d98532	FALSE	*	fast:2020
2	AWS	Multi-AZ OOTB	viya4-iac-aws: PR viya4-deployment: 6.12.0	N/A	v1.27.4-eks-2d98532	TRUE	*	fast:2020
3	AWS	Multi-AZ > Stop Viya > Single-AZ > Start Viya	viya4-iac-aws: 7.2.1 viya4-deployment: 6.12.0	viya4-iac-aws: PR viya4-deployment: 6.12.0	v1.26.7-eks-2d98532	FALSE	*	fast:2020	pods pending
4	AWS	Multi-AZ > Stop Viya > Multi-AZ > Start Viya	viya4-iac-aws: 7.2.1 viya4-deployment: 6.12.0	viya4-iac-aws: PR viya4-deployment: 6.12.0	v1.27.4-eks-2d98532	TRUE	*	fast:2020	pods all running
5	AWS	Single-AZ > Stop Viya > Multi-AZ > Start Viya	viya4-iac-aws: PR viya4-deployment: 6.12.0	viya4-iac-aws: PR viya4-deployment: 6.12.0	v1.26.7-eks-2d98532	FALSE > TRUE	*	fast:2020	this tests switching the enable_multi_zone flag while only using the PR code
6	AWS	Multi-AZ > Stop Viya > Single-AZ > Start Viya	viya4-iac-aws: PR viya4-deployment: 6.12.0	viya4-iac-aws: PR viya4-deployment: 6.12.0	v1.27.4-eks-2d98532	TRUE > FALSE	*	fast:2020	this tests switching the enable_multi_zone flag while only using the PR code, pods pending

[dhoucgitter]

LGTM