docs(tutorials): expand cluster templates tutorial for provisioning

Refocus the cluster templates tutorial on standardizing
cluster provisioning, maintenance, and upgrades using
Palette and Terraform.

Add end-to-end workflows that provision dev and prod
clusters from a shared template, apply maintenance
policies, update profile versions, and roll out upgrades
across clusters.

Extend coverage to AWS and Azure, clarify prerequisites
and cost implications, and align titles, metadata, and
steps with real-world provisioning and upgrade scenarios.

Author: brent-eritou