Support gRPC and gRPC-Web protocol in metrics

[longit644]

What does this PR do?

Add grpc, grpcweb as a protocol to metrics when incoming request is a gRPC or gRPC-Web request and use gRPC Code instead of HTTP Status for code.

Motivation

To enhance gRPC, gRPC-Web metrics.

Supersedes #9415

More

• [ ] Added/updated tests
• [ ] Added/updated documentation

Additional Notes

Sample prometheus metrics

traefik_router_request_duration_seconds_bucket{code="Unauthenticated",method="POST",protocol="grpc",router="...",service="...",le="0.005"} 2

[kevinpollet]

Hello @longit644,

Thanks for opening the pull request,

We rebased the pull request but we are unable to push those commits because of missing rights. Our CI tools will also not work properly because of those missing rights.

This is because you forked your organization repository which makes your personal fork inherits the organization's fork rights.

Please could you do the following:

1. delete your current fork (https://github.com/longit644/traefik)
2. create a new Traefik fork from the Traefik repository (https://github.com/traefik/traefik/fork)
3. push your local branch to this new fork
4. open a new pull request

[longit644]

Hello @kevinpollet,

Thanks for your guide. I opened a new pull request here: #9483.