added new lab backend-pool-load-balancing-terraform

[HoussemDellai]

Purpose

New lab for the scenario backend-pool-load-balancing but with Terraform.
All the changes are in the folder backend-pool-load-balancing-terraform.
It respects most of the structure of the other labs.

However, there are some differences:

1. This new lab uses Azure AI Services instead of Azure OpenAI resources.
2. It uses the GPT-4o models instead of the GPT-3.5.
3. Due to the model availability, GPT-4o was deployed with GlobalStandard instead of Standard.
4. This new lab uses APIM with SKU BasicV2 created using Terraform AZAPI instead of AzureRM because it is not yet available.
5. To apply the renaming of the policy, it is done directly in the Terraform template.
6. These Terraform templates doesn't use modules (could be implemented later).

Does this introduce a breaking change?

[ ] Yes
[x] No

[ ] Bugfix
[ x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe: