Testing/P2P: Refactor testing files with better comments in lib_p2p (test conventions changed)
Issue #900 (closed) about improving comments for testing files. A new convention exists to document test files (see a draft in #900 (closed), which has been discussed in testing meeting Sept 24, 2020).
This MR is a follow-up of !2115 (merged) as the convention for testing files has changed.
Edited by Hai Nguyen Van