CI: vanilla CO-RE BPF vs custom CO-RE BPF

[erthalion]

It's necessary to have an internal toggle to be able to switch between custom &
vanilla CO-RE BPF implementation. We could use this to cross-verify CI results
at the deeper level than just matching process name or opened port: all stable
resources could be compared, e.g. actual fds, uid/gid, sinsp event sequence
etc.

Investigate if it's possible to implement such comparison within the framework
of current CI with minimal changes.

Part of #1320