fix lua result serialization causing various issues

for example, loading a library which returns a table of functions would
fail with an inexplicable (to the user) error about serialization. This
is now fixed. We no longer use a single result type, instead there are
void results and normal results, and the former simply never has to
worry about the result.

This was likely causing even more issues; if the `sol::object` was
populated before, it hitting the dtor in another path would, again, like
we've seen before, corrupt the lua stack.

src/TConsole.cpp

@@ -810,7 +810,7 @@ void TConsole::InitializeCommandline() {
                     auto Future = mLuaEngine->EnqueueScript(mStateId, { std::make_shared<std::string>(TrimmedCmd), "", "" });
                     Future->WaitUntilReady();
                     if (Future->IsError()) {
-                        auto Snapshot = Future->GetDetachedSnapshot();
+                        auto Snapshot = Future->GetSnapshot();
                         beammp_lua_error("error in " + mStateId + ": " + Snapshot.ErrorMessage);
                     }
                 }