Investigate RBAC for AKS

[schnerring]

With v3 of the azurerm provider, role_based_access_control_enabled defaults to true.

Upgrading required to following to prevent cluster re-creation.

infrastructure-core/core/aks.tf

Lines 22 to 23 in bc4d9aa

	# TODO: defaults to true since azurerm v3
	role_based_access_control_enabled = false

Investigate whether implementing RBAC is worth re-creating the cluster.