Early Attestation and Measurement Architecture

[stefano-garzarella]

As I had anticipated in past meetings, we are working on a proposal for early attestation in SVSM especially to support a persistent state to be used with vTPM and UEFI variables. The shared document is here: https://docs.google.com/document/d/11ZsxP8jsviP3ddp9Hrn0rf6inttNw_Pbnz0psXlxlPs

When we have a good version, we will open a PR to continue the discussion and move the document to Documentation/docs in this repo, along with an initial implementation.

Any comments, help is more than welcome both here and in the shared gdoc.

Thanks Dionna Glaze, Elena Reshetova, Tyler Fanelli, Daniel Berrange, Vivek Goyal, Oliver Steffen for the help so far!