Rename net/ip.{cpp,hpp} to net/ip_packet.{cpp,hpp}.
(Doing this in two commits because I want to repurpose ip.hpp/ip.cpp,
and want git to figure out the history properly).
This commit reflects changes to clang-format rules. Unfortunately,
these rule changes create a massive change to the codebase, which
causes an apparent rewrite of git history.
Git blame's --ignore-rev flag can be used to ignore this commit when
attempting to `git blame` some code.
