Enable log macros to work with no args (#4475)

This is enabled by the C++20 __VA_OPT__ feature.
Uses of "{}" format string were updated.
Some warning suppressions were required for older clang versions.
Also improve codegen of wpi::Logger::Log(), frc::ReportError(), and frc::MakeError();
these generate better and less redundant code if they use fmt::string_view for the
format string instead of templating on it.

wpiutil/src/main/native/thirdparty/llvm/cpp/llvm/ErrorHandling.cpp

@@ -163,7 +163,7 @@ void wpi::wpi_unreachable_internal(const char *msg, const char *file,
   std::fputs("UNREACHABLE executed", stderr);
   if (file)
     fmt::print(stderr, " at {}:{}", file, line);
-  fmt::print(stderr, "{}", "!\n");
+  fmt::print(stderr, "!\n");
   abort();
 #ifdef LLVM_BUILTIN_UNREACHABLE
   // Windows systems and possibly others don't declare abort() to be noreturn,