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/uber/jaeger-client-go/header.go

@@ -38,7 +38,8 @@ type HeadersConfig struct {
 	TraceBaggageHeaderPrefix string `yaml:"traceBaggageHeaderPrefix"`
 }
 
-func (c *HeadersConfig) applyDefaults() *HeadersConfig {
+// ApplyDefaults sets missing configuration keys to default values
+func (c *HeadersConfig) ApplyDefaults() *HeadersConfig {
 	if c.JaegerBaggageHeader == "" {
 		c.JaegerBaggageHeader = JaegerBaggageHeader
 	}