Multiple web sources for multiple extensions overwrites s3 folder

**Describe the bug**

We don't support multiple UIs as part of the same project.

Creating a project with multiple extensions and UIs will overwrite the s3 folder instead of returning an error.

**Workaround**
Quoting @shazron

The tooling doesn't have the concept of partitioning the S3 bucket for different web extensions because of the above rule. When uploading to S3, it will empty out the namespace's partition every time thus this is what you are seeing.
One possible workaround is to use aio app use and create/use a different secondary workspace to deploy your other web extension (skip deploying actions), and use the primary workspace for your main web extension and actions. There might be CORS issues with the secondary workspace web assets with the primary workspace actions however, but you can get around this by setting the appropriate headers: https://developer.adobe.com/app-builder/docs/guides/deployment/setting-response-headers/

Reproduce the deployment described for a project with multiple extensions and UIs, then start with the `aio app use` workspace behavior and the tooling's S3 upload path. Confirm where the namespace is emptied and define the completed behavior as returning an error instead of overwriting another extension's folder.

Written by the indexing model from the issue text.