AWS Toolkit adding routes nat gateways don't show up

**Describe the bug**
When adding routes to a route table through AWS toolkit. NAT gateways don't show up.
You can use use the eni of the nat instance but interestingly this doesn't display a name in aws toolkit.
The NAT gateway route does show up on cosole.
e.g. route table in AWS toolkit
10.10.0.0/16 | local | active
0.0.0.0/0 | | active

**To Reproduce**

**Expected behavior**

Ideally the nat gateways should display or the very least its eni.

**Screenshots**

**Computer (please complete the following information):**

- Windows Version: Microsoft Windows Server 2019 Datacenter
- Visual Studio Version: Microsoft Visual Studio Community 2019
Version 16.6.1
- AWS Toolkit for Visual Studio Version: 2017/2019

**Additional context**

Start in the AWS Toolkit's Amazon VPC route-table flow and reproduce the issue by adding a NAT gateway route. Compare the route-table display with the AWS web console, including the NAT gateway or its ENI. Done means the route target is selectable or displayed correctly in the Toolkit.

Written by the indexing model from the issue text.