Reporting DRTM/AEM status in QubesOS

[macpijan]

A PoC has been presented during QubesOS summit 2024: https://youtu.be/5ieNhbLLTIU?si=CDpmkUO187bar8JV (see screenshot below).

Relevant code changes:

• Xen - exposing TXT capability
• Security report UI changes
• Security report backend changes (HCL)

Xen change should be consulted with Xen maintainers, QubesOS changes - QubesOS maintainers. We should also consider AMD case. But the end goal remains the same - to expose the DRTM and/or AEM in the QubesOS Security UI.