Generate configuration names and config.vars files

[glennmusa]

Description

Previously, the names of Mission LZ and individual terraform configuration resources (the resource groups that store terraform state, and the Service Principal and Key Vault that permits access to the subscriptions) were known only at resource creation time.

This change allows us to derive these names at any time given a mlz_tf_cfg.var file and aide in CI/CD efforts, or any other post-configuration deployment activity.

Issue reference

The issue this PR is associated with: #54

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles or validates correctly
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• All tests pass (manual and automated)
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• Relevant issues are linked to this PR