fix: Add variables to configure availability zones in aks cluster

[GiovanniMancini]

Add variables to configure availability zones of

• system node pool
• user node pool

in aks cluster.

List of changes

Motivation and context

Backward compatibility

Type of changes

• [ ] Add new module
• [x] Update existing module
• [ ] Remove existing module

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Other information

Run checks

Useful commands to run checks on local machine

bash .utils/terraform_run_all.sh init local
pre-commit run -a

[github-actions[bot]]

:tada: This PR is included in version 4.3.1 :tada:

The release is available on GitHub release

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