Migrate gitlab-haproxy Chef secrets from GKMS to Hashicorp Vault

Migrate gitlab-haproxy Chef secrets from GKMS to Hashicorp Vault.

• Identify related cookbooks and add Vault configs
• Modify related cookbooks to fetch secrets from Vault
• Copy gitlab-haproxy environment secrets to appropriate path in Vault.
• Update Chef roles with the necessary config to use Vault secrets.

Merge Requests

• Adding Vault configurations for gitlab-haproxy cookbook
• Add Vault backend for gitlab-haproxy cookbook secrets
• Adding Vault role for load balancer roles gstg gprd pre