[WIP] Implement cluster registration workflows via Shepherd/golang

[git-ival]

Features:

• "Natural" sorting of slices based on some string contained in each element
  • Currently used for imported downstream_cluster_templates to trigger import cluster registration workflow in-order based on name
• Batched, sequential and concurrent cluster registration
  • Imported Clusters: fully functional
  • Provisioned Clusters: implemented, not yet tested
  • Custom Clusters: fully functional
• Idempotency for all cluster registrations via custom state handling logic within dartboard
  • Uses the newly-introduced ClusterStatus struct that contains basic state information for each Cluster that has been sent to the cluster registration batch runner
• Currently functional for Harvester envs, AWS envs need further tuning to be considered fully functional

Closes #72

[Copilot]

Pull request overview

This PR implements cluster registration workflows via Shepherd/golang, enabling batch processing of imported, provisioned, and custom Kubernetes clusters with idempotent state management.

Key changes:

• Introduces custom cluster support with machine pool configurations and validation
• Implements concurrent batch runner with state persistence for cluster registration
• Removes context.Context parameters from tofu functions, adds state management infrastructure

Reviewed changes

Copilot reviewed 44 out of 45 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tofu/modules/harvester/node/outputs.tf	Renamed output from public_address to public_ip for consistency
tofu/modules/generic/test_environment/variables.tf	Added custom cluster support with machine pools and validations
internal/tofu/tofu.go	Refactored to remove context parameters, added custom cluster types and helper functions
internal/actions/batchrunner.go	New concurrent batch runner for cluster operations with state management
internal/actions/rancher.go	New cluster registration workflows (import, provision, register custom)
internal/actions/handlestate.go	New state persistence for cluster registration idempotency
internal/harvester/*	New package ported from harvester-cli for VM management
internal/dart/recipe.go	Extended with cluster template and config types
cmd/dartboard/subcommands/*	Updated CLI to support new workflows with skip flags

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