Update split SDK to 6.0.2 to fix sync bug (#17060)

* Update split SDK to 6.0.2 to fix sync bug

* Vendor and tidy

vendor/github.com/splitio/go-toolkit/v4/common/refutil.go

@@ -0,0 +1,74 @@
+package common
+
+// StringRef returns ref
+func StringRef(str string) *string {
+	return &str
+}
+
+// StringFromRef returns original value if not empty. Default otherwise.
+func StringFromRef(str *string) string {
+	if str == nil {
+		return ""
+	}
+	return *str
+}
+
+// IntRef returns ref
+func IntRef(number int) *int {
+	return &number
+}
+
+// IntFromRef returns 0 if nil, dereferenced value otherwhise.
+func IntFromRef(ref *int) int {
+	if ref == nil {
+		return 0
+	}
+	return *ref
+}
+
+// Int64Ref returns ref
+func Int64Ref(number int64) *int64 {
+	return &number
+}
+
+// Int64FromRef returns value
+func Int64FromRef(number *int64) int64 {
+	if number == nil {
+		return 0
+	}
+	return *number
+}
+
+// Int64Value kept to prevent breaking change. TODO: Deprecate in v4
+func Int64Value(number *int64) int64 {
+	return Int64FromRef(number)
+}
+
+// Float64Ref returns ref
+func Float64Ref(number float64) *float64 {
+	return &number
+}
+
+// IntRefOrNil returns ref
+func IntRefOrNil(number int) *int {
+	if number == 0 {
+		return nil
+	}
+	return IntRef(number)
+}
+
+// Int64RefOrNil returns ref
+func Int64RefOrNil(number int64) *int64 {
+	if number == 0 {
+		return nil
+	}
+	return Int64Ref(number)
+}
+
+// StringRefOrNil returns ref
+func StringRefOrNil(str string) *string {
+	if str == "" {
+		return nil
+	}
+	return StringRef(str)
+}