feat: add delegated routing metrics

[guseggert]

Example log output:

Enable warn level:

$ ipfs log level 'service/client/delegatedrouting' WARN

Output:

2022-10-19T08:22:28.009-0400    WARN    service/client/delegatedrouting client/metrics.go:51    received delegated routing error        {"Error": "sending HTTP request: Get \"http://127.0.0.1:5098/reframe?q=...\": dial tcp 127.0.0.1:5098: connect: connection refused"}

Metrics:

$ curl -s http://127.0.01:5001/debug/metrics/prometheus | grep -i delegated
# HELP delegated_routing_duration The time to complete an entire request
# TYPE delegated_routing_duration histogram
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="1"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="2"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="5"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="10"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="20"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="50"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="100"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="200"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="500"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="1000"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="2000"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="5000"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="10000"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="20000"} 1
delegated_routing_duration_bucket{error="Net",name="ContentRoutingClient.FindProvidersAsync",le="+Inf"} 1
delegated_routing_duration_sum{error="Net",name="ContentRoutingClient.FindProvidersAsync"} 0
delegated_routing_duration_count{error="Net",name="ContentRoutingClient.FindProvidersAsync"} 1
# HELP delegated_routing_requests The number of requests made
# TYPE delegated_routing_requests counter
delegated_routing_requests{error="Net",name="ContentRoutingClient.FindProvidersAsync"} 1