Replaces custom logging system with spdlog-based oxen logging. This
commit mainly replaces the backend logging with the spdlog-based system,
but doesn't (yet) convert all the existing LogWarn, etc. to use the new
format-based logging.
New logging statements will look like:
llarp::log::warning(cat, "blah: {}", val);
where `cat` should be set up in each .cpp or cluster of .cpp files, as
described in the oxen-logging README.
As part of spdlog we get fmt, which gives us nice format strings, where
are applied generously in this commit.
Making types printable now requires two steps:
- add a ToString() method
- add this specialization:
template <>
constexpr inline bool llarp::IsToStringFormattable<llarp::Whatever> = true;
This will then allow the type to be printed as a "{}" value in a
fmt::format string. This is applied to all our printable types here,
and all of the `operator<<` are removed.
This commit also:
- replaces various uses of `operator<<` to ToString()
- replaces various uses of std::stringstream with either fmt::format or
plain std::string
- Rename some to_string and toString() methods to ToString() for
consistency (and to work with fmt)
- Replace `stringify(...)` and `make_exception` usage with fmt::format
(and remove stringify/make_exception from util/str.hpp).
