Expose latency metrics for gRPC services in Prometheus

[jjngx]

Is your feature request related to a problem? Please describe.

Currently it's not possible to gather latency metrics for gRPC services.

Describe the solution you'd like

The feature would allow to gather the metrics when NIC starts with relevant flags on (prometheus and latency).

Describe alternatives you've considered

N/A

Additional context

currently logged issue

PR to remove log line: https://github.com/nginxinc/kubernetes-ingress/pull/6125

### POC Tasks

### Implementation Tasks

[github-actions[bot]]

Hi @jjngx thanks for reporting!

Be sure to check out the docs and the Contributing Guidelines while you wait for a human to take a look at this :slightly_smiling_face:

Cheers!

[shaun-nx]

@jjngx do you know if there is still value in allowing latency metrics to be exposed through the prometheus exporter?