Add util to lookup private key from address (for benchmark)

client/utils.go

@@ -0,0 +1,12 @@
+package client
+
+import "github.com/simple-rules/harmony-benchmark/crypto/pki"
+
+var AddressToIntPriKeyMap map[[20]byte]int  // For convenience, we use int as the secret seed for generating private key
+
+func init() {
+	AddressToIntPriKeyMap := make(map[[20]byte]int)
+	for i := 0; i < 10000; i++ {
+		AddressToIntPriKeyMap[pki.GetAddressFromInt(i)] = i
+	}
+}