terraform upgrade to 1.5.7

[sblair-metrostar]

Fixes #1913

What does this implement/fix?

Put a x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features not to work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

• Did you test the pull request locally?
• Did you add new tests?

Any other comments?

Only tested on AWS so far. Needs to be run in each supported cloud environment.

[iameskild]

I successfully tested this branch on an existing Digital Ocean deployment.

Side note: This version of TF seems to be significantly faster 🎉

[iameskild]

Testing this with GCP failed because of the deprecation of module_variable_optional_attrs. Removing the the provider.tf file altogether seems to resolve the issue without any known side-effects; I'm not sure why we were using it in the first place.

I'm removing this provider.tf file in #2010.

[iameskild]

Okay deploying this branch on Azure was also successful. This is ready to be merged 🎉