tdx: allow limiting verification to explicit PIIDs

[burgerdev]

This PR adds a new field to the TDX reference values, AllowedPIIDs, that allows limiting the platform instance IDs (PIIDs) that are allowed by a manifest. Essentially, this can be used to only allow a specific, enumerated set of machines to participate in a Contrast deployment.

If the list of allowed PIIDs is empty (the default), all TDX machines are allowed, making this change backwards-compatible.

Conceptually, this is closely related to #1952.

[github-actions]

Do the documentation changes need to be backported?

Changes to /docs/docs won't be visible until the next release.
If you are fixing something in the docs that should be immediately visible, the changes needs to be made to both /docs/docs and /docs/versioned_docs/version-X.Y, where X.Y is the version of the latest minor release.
This can be done in this same PR.

• Yes, this should be backported to the current version of the docs.
• No, the PR only contains docs changes relevant for future versions.

[github-actions]

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2026-01-13 07:30 UTC

[katexochen]

needs PR description

[burgerdev]

All comments should be addressed now, ptal.

[thomasten]

I reviewed the first and the docs commit, which LGTM