Static schema support for Terraform Test and Mock files

[dbanck]

• Requires Static schema support for Terraform Test and Mock files terraform-ls#1782

This PR adds Terraform Test & Mock file support. It adds the language configuration for test and mock files and registers the document selectors, so test files are picked up by the language server.

[jpogran]

🚢

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.