refactor: Extract util/exception from util/system

This is a minimal extraction of a single function, but also the only use
of std::exception in util/system.

The background of this commit is an ongoing effort to decouple the
libbitcoinkernel library from the ArgsManager defined in system.h.
Moving the function out of system.h allows including it from a separate
source file without including the ArgsManager definitions from system.h.

0 files changed, 0 insertions, 0 deletions