Add Prometheus metrics

[orishoshan]

Today, only the network-mapper exposes Prometheus metrics (default Golang metrics as well as custom metrics).

Proposal: Expose Prometheus default Golang metrics as well as custom metrics that are in-line with the telemetry (i.e. network policies created, intents reconciled, and so on: search for telemetrysender).

[seeker815]

Hey @orishoshan , came across the project and would like to take this up, thanks

[orishoshan]

@seeker815 Please do! If you need any guidance, feel free to reach out to me on the community Slack. You can find an example for how to add Prometheus metrics in the network-mapper repository: https://github.com/otterize/network-mapper/blob/main/src/mapper/pkg/prometheus/metrics.go