feat: Support spotToSpotConsolidation per nodepool

[Fs02]

Fixes #1449

Description

• Adds spotToSpotConsolidation field to NodePool's Disruption spec, allowing per-NodePool control over spot-to-spot consolidation
• When set to true/false, overrides the global SpotToSpotConsolidation feature gate for that NodePool
  When unset, falls back to the global feature gate behavior
• For multi-node consolidation involving multiple NodePools, ALL source NodePools must have spot-to-spot enabled for consolidation to occur

How was this change tested?
Use kind and kwook to create nodepools, one with spotToSpotConsolidation enabled and the other one disabled.
Run a simple test by scaling out and scaling in test pods and checking the Unconsolidatable events.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Fs02 / name: Surya Asriadie (2b75bbf, a86d612, ddce3df)

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[Fs02]

@DerekFrank @tallaxes please take a look 🙏