Add some debug info to the periodical map cleanup process. Push debug
information through the events perf buffer by using newly added
map_clean_event.
The old user space map cleanup process had some simple debug
information that was lost when transitioning to using bpf_iter
instead. Therefore, add back similar (but more extensive) debug
information but now collected from the BPF-side. In addition to stats
on entries deleted by the cleanup process, also include stats on
entries deleted by ePPing itself due to matching (for timestamp
entries) or detecting FIN/RST (for flow entries)
Signed-off-by: Simon Sundberg <simon.sundberg@kau.se>
