Adding details on how the Red Team will manage Caldera customizations per operation

Why is this change being made?

This MR explains how we use Mitre Caldera in red team operations, and specifically proposes a new method for developing adversary capabilities per operation.

Hopefully this will allow our team to better collaborate on Caldera abilities across separate, often disposable, installations of Caldera.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
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• Assign reviewers for this change to the correct DRI(s)
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