feat: Prompt users to use TFC workaround

[mildaniel]

Which issue(s) does this change fix?

N/A

Why is this change necessary?

Prompt users to use the Terraform Cloud workaround when they encounter the TFC error.

How does it address the issue?

1. Fixes the loading dot subprocess loader to store and return data from stderr
2. Reads the stderr data, checking for the TFC error message and returns an appropriate help message if found.

What side effects does this change have?

N/A

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• Add input/output type hints to new functions/methods
• Write design document if needed (Do I need to write a design document?)
• Write/update unit tests
• Write/update integration tests
• Write/update functional tests if needed
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.