feat: improve otel to promql compat

[ernado]

Following metric, if exporter as otlp

sentRequestsCount, err := meter.Int64Counter("oteldemo.client.sent_requests")
if err != nil {
	return errors.Wrap(err, "create counter")
}

Exported as otlp:

oteldemo_client_sent_requests{}

Exported as prometheus:

oteldemo_client_sent_requests_total{}