message: Add assertion that at most 1 stack element is returned in execute
diff: @@ -1456,7 +1456,8 @@ execution_result execute(Instance& instance, FuncIdx func_idx, span<const uint64
  }
  end:
  - assert(pc == &code.instructions[code.instructions.size()] || trap);
  + // WebAssembly 1.0 allows at most one return variable.
  + assert(trap || (pc == &code.instructions[code.instructions.size()] && stack.size() <= 1));
  return {trap, {stack.rbegin(), stack.rend()}};
  }
  