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/interface.go

@@ -0,0 +1,53 @@
+package common
+
+// AsIntOrNil returns ref
+func AsIntOrNil(data interface{}) *int {
+	if data == nil {
+		return nil
+	}
+
+	number, ok := data.(int)
+	if !ok {
+		return nil
+	}
+	return IntRef(number)
+}
+
+// AsInt64OrNil returns ref
+func AsInt64OrNil(data interface{}) *int64 {
+	if data == nil {
+		return nil
+	}
+
+	number, ok := data.(int64)
+	if !ok {
+		return nil
+	}
+	return Int64Ref(number)
+}
+
+// AsFloat64OrNil return ref
+func AsFloat64OrNil(data interface{}) *float64 {
+	if data == nil {
+		return nil
+	}
+
+	number, ok := data.(float64)
+	if !ok {
+		return nil
+	}
+	return Float64Ref(number)
+}
+
+// AsStringOrNil returns ref
+func AsStringOrNil(data interface{}) *string {
+	if data == nil {
+		return nil
+	}
+
+	str, ok := data.(string)
+	if !ok {
+		return nil
+	}
+	return StringRef(str)
+}