Implement endpoints for uploading version state

The newer versions of terraform attempt to create an empty state version and then upload the state separately (in both terraform and JSON format). You can see the code here: https://github.com/hashicorp/go-tfe/blob/main/state_version.go#L284

It would be nice if terrarun supported this.

It would require 3 new endpoints:

Additional attributes for the state version that point to those endpoints:

And the status attribute (possibly added in #10) with pending, finalized and discarded depending on the state upload.