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/Unknwon/com/math.go

@@ -14,12 +14,12 @@
 
 package com
 
-// PowInt is int type of math.Pow function. 
+// PowInt is int type of math.Pow function.
 func PowInt(x int, y int) int {
 	if y <= 0 {
 		return 1
 	} else {
-		if y % 2 == 0 {
+		if y%2 == 0 {
 			sqrt := PowInt(x, y/2)
 			return sqrt * sqrt
 		} else {