Generte the full system SBOM for the end2end example

[pahmann]

The AGL needlefish already can generate the SBOM using yocto tooling. A full system SBOM should also include Xen and Zephyr. In this task it should be checked, how to generate the SBOM for Xen and Zephyr. It may include to build Xen and Zephyr directly in yocto rahter than with e.g. west as for Zephyr. If the demo can be built with all elements created from Yocto the SBOM generation may become easier and consistent.

[pahmann]

This can be a good topic after qemu system is reproducible.

[pahmann]

Drafting first thoughts inside this document: https://docs.google.com/document/d/12jcC9CrGHlYwLBlFql6VLCsOmcl63paih2kj_1J55D