replace dep with go modules (#16017)

- guide shamelessly stolen from prometheus/prometheus
- updates local interface of oauth exchange
- updates local impl of hclogger
- bump jaeger client version

closes #16088

vendor/github.com/prometheus/common/model/metric.go

@@ -21,7 +21,6 @@ import (
 )
 
 var (
-	separator = []byte{0}
 	// MetricNameRE is a regular expression matching valid metric
 	// names. Note that the IsValidMetricName function performs the same
 	// check but faster than a match with this regular expression.