Feature/tf workspace key prefix support

[mbordash2]

Adding support for Terraform state workspace_key_prefix option.

Summary

Updated Terraform backend config data model to support workspace_key_prefix.

Why This Is Needed

closes #1595

What Changed

Added

Support for new Terraform backend config option.

Checklist

• Have you followed the guidelines in our Contribution Requirements?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Does your submission pass tests?
• Have you linted your code locally prior to submission?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?
• Have you updated documentation, as applicable?

[codecov]

Codecov Report

Merging #1757 (0948a72) into master (915f30e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1757   +/-   ##
=======================================
  Coverage   90.17%   90.17%           
=======================================
  Files         247      247           
  Lines       15424    15425    +1     
=======================================
+ Hits        13909    13910    +1     
  Misses       1515     1515           

Impacted Files	Coverage Δ
runway/module/utils.py	100.00% <ø> (ø)
runway/config/models/runway/options/terraform.py	100.00% <100.00%> (ø)

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[mbordash2]

All CI/CD tests are now passing.