EC2 Instance Attestation

[arianvp]

End goal is that all the code in https://github.com/aws/nitrotpm-attestation-samples/tree/main/nix is upstreamed in way that is idiomatic and easy to use.

Will add more TODOs as I think of 'em

• Drop BIOS Support and only build UEFI images, as T3 is now in the free tier #322 needed to we're EFI only
• Merge Various repart image simplifications nixpkgs#485954 so no need for nixos-generators
• Maybe move RegisterImage options to NixOS Module options instead of upload-ami flags