Add metrics for provider requests

[aramase]

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
We have metrics today for the csi driver. Now that the provider runs as a standalone pod, we can enable metrics for the provider.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Secrets Store CSI Driver version: (use the image tag):
• Azure Key Vault provider version: (use the image tag):
• Kubernetes version: (use kubectl version):
• Cluster type: (e.g. AKS, aks-engine, etc):