eBPF for Windows should support signed ELF files

Summary:
eBPF for Windows should support signature enforcement on ELF files containing eBPF programs. eBPF for Windows could then be configured to only permit loading of ELF files signed by key chaining up to a specific set of trusted roots.

Need to write up a detailed proposal for this prior first.

Existing proposals [Toward signed BPF programs](https://lwn.net/Articles/853489/)

Start by reading the linked “Toward signed BPF programs” proposal and the issue’s requirement for signature enforcement on ELF files containing eBPF programs. Define how trusted roots and key chaining should be configured, and document the detailed proposal needed before implementation can begin.

Written by the indexing model from the issue text.