update pipeline to run aks free vs. standard test

[anson627]

This pull request includes several updates to the Azure performance evaluation pipeline and the steps for collecting cloud information and setting Terraform input variables. The most important changes include modifying the stages to add new tiers, updating the collect-cloud-info.yml to include SKU tier information, and setting SKU tier in Terraform input variables.

Updates to Azure performance evaluation pipeline:

• pipelines/perf-eval/apiserver-benchmark-virtualnodes10-pods100.yml: Renamed the azure_eastus2 stage to azure_eastus2_free and added a new azure_eastus2_standard stage with appropriate parameters. [1] [2]

Collecting cloud information:

• steps/cloud/azure/collect-cloud-info.yml: Added the sku_tier argument to the cloud info collection script to capture the SKU tier of the AKS cluster.

Setting Terraform input variables:

• steps/terraform/set-input-variables-azure.yml: Included SKU_TIER in the environment variables to be set, which should be defined by the matrix.