DynamoDB Table scans are not returning all items

**Describe the bug**
There's a serious bug in the AWS Explorer add on for Visual Studio 2019.

When Scanning a table with a specific condition it returns no/incomplete results in AWS Explorer. However when running the Scan through the browser console or an API it returns the correct list of results.

It appears to be out of sync, for example I see 5 entries returned by the web console in one Scan, where as AWS explorer returns only 4.
For another table the web console returns 1 entry where as AWS explorer returns none!

Example:
When I use the AWS Explorer from Visual Studio 2019, it returns only 4 objects (it's missing an entry from yesterday): https://drive.google.com/file/d/1iBcXtjLcQwZ7qbYFyaHFvkHVaACu2dcT/view?usp=sharing
When I use the AWS Web Console, it returns 5 objects (the correct number): https://drive.google.com/file/d/1_eas_PHq66Xlu95qqcDwF3Iq30aBpPBm/view?usp=sharing

This doesn't happen for every attribute value being matched by the Scan. What I mean is, if I change the value being searched by the "Scan" filters (in this screenshot the value is xxx975), for some values it retrieves all the records in AWS Explorer, but for some values (like the one in this screenshot xxx975), it's missing one record in the response.

BTW, this problem only happens with AWS Explorer. When using the same "Scan" via an API (in a .NET application) or through the Web Console it returns all the matching objects. It almost sounds like the results are not being completely enumerated by AWS Explorer after the Scan is completed and consequently it's missing a few records.

More details provided here: Screenshot are available here: https://forums.aws.amazon.com/thread.jspa?messageID=956512

**Expected behavior**
Return all matching items as returned by the Web Console

**Screenshots**
Screenshot are available here: https://forums.aws.amazon.com/thread.jspa?messageID=956512

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

- Windows Version: Windows 10
- Visual Studio Version: 1.18.1.0
- AWS Toolkit for Visual Studio Version: 16.7.3

**Additional context**

Reproduce the filtered DynamoDB Scan in AWS Explorer for Visual Studio 2019, then compare its results with the AWS web console or a .NET API call. Trace how the Explorer enumerates Scan results and pagination; done means every matching item is returned consistently across the same filter.

Written by the indexing model from the issue text.