Separate variables for default and internal nodepools VM sizes

All Submissions:

---

• [YES] Have you added an explanation of what your changes do and why you'd like us to include them?
• [NO] I have updated the documentation accordingly.
• [YES] My code follows the code style of this project.

Current Behavior or Linked Issues

---

Added a separate variable to set different VM sizes for default and internal nodepools and renamed the variable aks_agent_vm_size for a clear description.

Does this introduce a breaking change?

---

• [NO]

Other information

---

devops/custom_pipelines/infrastructure/service-resource.tfvars

@@ -23,7 +23,8 @@ resource_tags = {
 }
 
 # Kubernetes Settings
-aks_version_prefix = "1.27"
-aks_agent_vm_size  = "Standard_E4s_v3"
-aks_agent_vm_count = "5"
-subnet_aks_prefix  = "10.10.2.0/23"
+aks_version_prefix         = "1.27"
+aks_agent_vm_size_default  = "Standard_E4s_v3"
+aks_agent_vm_size_internal = "Standard_E4s_v3"
+aks_agent_vm_count         = "5"
+subnet_aks_prefix          = "10.10.2.0/23"