feat: add NestedVirtualization to CPUOptions in v1beta1 and v1beta2 APIs (backport release-2.9)

[jhjaggars]

Summary

Backport of #5874 to release-2.9.

• Add NestedVirtualizationPolicy type and NestedVirtualization field to CPUOptions in api/v1beta2/types.go
• Add AWSConfidentialComputePolicy, NestedVirtualizationPolicy types and CPUOptions struct as a native field in api/v1beta1/types.go and api/v1beta1/awsmachine_types.go, enabling consumers (e.g. HyperShift) to set CPU options directly via the v1beta1 API without relying on the annotation-based restore pattern
• Remove manual CPUOptions restore lines from v1beta1 conversion files — auto-generated conversion now handles the field
• Add NestedVirtualization switch in getInstanceCPUOptionsRequest() mapping to EC2 SDK NestedVirtualizationSpecification
• Bump github.com/aws/aws-sdk-go-v2/service/ec2 to v1.288.0 for CpuOptionsRequest.NestedVirtualization support
• Regenerate deepcopy, conversion, and CRD manifests

Test plan

• make test passes locally
• make lint passes with 0 issues
• Verify AWSMachineTemplate with cpuOptions.nestedVirtualization: enabled accepted by v1beta1 webhook

🤖 Generated with Claude Code

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