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

pkg/plugins/hclog-wrapper.go

@@ -1,6 +1,8 @@
 package plugins
 
 import (
+	"io"
+	"io/ioutil"
 	"log"
 
 	glog "github.com/grafana/grafana/pkg/log"
@@ -47,3 +49,10 @@ func (lw LogWrapper) ResetNamed(name string) hclog.Logger {
 func (lw LogWrapper) StandardLogger(ops *hclog.StandardLoggerOptions) *log.Logger {
 	return nil
 }
+
+func (lw LogWrapper) SetLevel(level hclog.Level) {}
+
+// Return a value that conforms to io.Writer, which can be passed into log.SetOutput()
+func (lw LogWrapper) StandardWriter(opts *hclog.StandardLoggerOptions) io.Writer {
+	return ioutil.Discard
+}