attesters: add NVIDIA GPU evidence plugin

[cowbon]

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[jraman567]

Hi Tom,

Thanks for the PR! I left some comments.

Thank you,
Jag

[cowbon]

Hi Tom,

Thanks for the PR! I left some comments.

Thank you, Jag

Hi @jraman567 , thanks for the review. The followings are the latest changes

• Renamed the attester/package to nvgpu.
• Simplified GPU JSON encoding and removed wire/CBOR helpers.
• Uses NVIDIA’s NVML nonce-size constant.
• Changed Valid to a value receiver.
• Moved the NVML availability probe to plugin initialization.
• Documented NVIDIA driver/runtime prerequisites.
• Updated the CDDL nonce encoding to match standard JSON base64.

[jraman567]

Thanks, @cowbon ! LGTM!

Please note the additional comments I left concerning value receiver.