DNS DoH: Use Chrome's fingerprint & keepAlivePeriod, Add header padding by default

https://github.com/XTLS/Xray-core/discussions/4430#discussioncomment-12374292

common/crypto/crypto.go

@@ -1,2 +1,15 @@
 // Package crypto provides common crypto libraries for Xray.
 package crypto // import "github.com/xtls/xray-core/common/crypto"
+
+import (
+	"crypto/rand"
+	"math/big"
+)
+
+func RandBetween(from int64, to int64) int64 {
+	if from == to {
+		return from
+	}
+	bigInt, _ := rand.Int(rand.Reader, big.NewInt(to-from))
+	return from + bigInt.Int64()
+}