docs: add/update docs for deployment policy & compartments

[t0mmylam]

Add documentation for DeploymentPolicy and Compartments

Adds comprehensive documentation for the DeploymentPolicy feature, including:

Documentation Added

• docs/deployment_policy.md: Complete guide covering:

  • Compartments with label selectors and budgets (count/percent-based)
  • Three rollout strategies (Fixed, Linear, Exponential) with parameters
  • Overlap resolution using 3-level safety heuristic (strategy → ceiling → name)
  • Budget rounding formula and behavior
  • Safety mechanisms (batchThreshold, failureThreshold, safetyLimit)
  • Migration path from legacy interruptionBudget
  • Integration with Skyhooks

• docs/metrics/README.md: Added rollout metrics section documenting 8 new Prometheus metrics for tracking compartment progress, batch state, and failures

• docs/README.md: Updated with links to deployment policy and metrics docs

Samples

• Added operator/config/samples/deploymentpolicy_v1alpha1_deploymentpolicy.yaml showing multi-tier rollout example with critical, production, staging, and test compartments
• Updated operator/config/samples/kustomization.yaml to include new sample

Key Features Documented

• Selector overlap resolution: Safety-first tie-breaking algorithm
• Budget rounding: ceiling = max(1, int(matched_nodes × percent/100))
• Strategy comparison: Fixed (safest) vs Linear vs Exponential (fastest)
• Safety limit behavior: Different failure handling before/after progress threshold