Document frequency of cloud access

[KashifSaadat]

We should include a page covering the points/frequency at which the terranetes controller accesses the Cloud providers (AWS, GCP, Azure), if it's only on user action (CRUD on resources), or other periodic background jobs (i.e. drift detection), and how these can be controlled (directing to docs on how to disable drift detection). Similarly for cost estimates, which external service(s) it calls and at what times / intervals.