Buildernet - Bump attested-tls-proxy to 2.0.1 and use 'portable' measurements

[ameba23]

Note this is a protocol breaking change meaning Builderhub also needs updating to latest version of attested-tls-proxy via the devops repo.

This updates the Buildernet branch to use the latest version of attested-tls-proxy, which supports specifying measurements as OS image hashes rather than TDX register values.

Edit: i realised there is an issue with this - Builderhub internally checks measurements given in HTTP headers rather than using attested-tls-proxy for validation. So it wont work as is.

These hashes are created from the build image using the Easy-TEE/attest CLI tool. A Makefile command is included to make it easier to run this. During attestation verification, the verifier computes the expected register values based on these hashes together with 'platform metadata' provided by the attester.

The idea is to avoid getting attestation failures when Google update their firmware, or we use a different zone or hardware configuration.

The release pipeline is updated to include these image hashes as a release asset.

I have tested that i can build the image and compute hashes, but not actually deployed a node and seen a successful attestation.

One thing that might be useful to be able to quickly see if we can verify measurements is to port #143 to trunk/buildernet so that we log measurement registers at boot.

Here are the hashes i get from building on this branch:

{
  "azure": null,
  "dcap": {
    "cmdline_hash": "cf0ee3a3339203ad6867a2c8726d20d182867a0d219f69a20c3fbad44181290cf920d8f4f40fb200a47cab06696d9888",
    "gpt_disk_guid_hash": "585c427b06446617e5d91cc05436f2ea46c5ff733261e6a7073785d5a5d13462527ad171d6efa706b44ca4268e69925f",
    "initrd_hash": "518bd1ff5dc4d6dbc644d2bb007f4a1fd73e6b0232fa5c3f3f6d5dff0b0ced1238a1ec34f09df3f18a5bafd2ba26c127",
    "kernel_authenticode": "3b2ec1ef0dcfd378f46a389de1c66b82176966acad81e4e7c6640cb3f3c62f018550db1eaa30ac1632b3d387e7465471",
    "uki_authenticode": "823b45cd4cd22222161ccb5d267325f48c156dd1be521059051c201efa96e6302e0aabd529335b46bdb1d43669f2f599"
  },
  "kind": "portable"
}