aws: Add NestedVirtualization cpu-option support

Evgeny Fedinrequested to merge
TFT-4505 into main

Add NestedVirtualization=enabled cpu-option support for AWS instances that require nested virtualization.

  • Auto-populate FlavorVirtualization.is_supported from the AWS ProcessorInfo.SupportedFeatures API field — no hardcoded instance family lists needed
  • Pass --cpu-options NestedVirtualization=enabled when virtualization.is_supported constraint is requested
  • Refactor cpu-options building to support both AmdSevSnp and NestedVirtualization dynamically
  • Add SupportedFeatures to APIInstanceTypeProcessorInfo TypedDict

Assisted-by: Claude Code

Related to TFT-4505

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