ddddce0e46 util: Replace boost::signals2 with std::function (MarcoFalke)
Pull request description:
This removes the `#include <boost/signals2/signal.hpp>` from `util.h` (hopefully speeding up the build time and reducing the memory usage further after #13634)
The whole translation interface is replaced by a function `G_TRANSLATION_FUN` that is set to nullptr in units that don't need translation. (Thus only set in the gui)
Tree-SHA512: 087c717358bbed8bdb409463e225239d667f1ced381abb10e7cd31a41dcdd2cebe20b43c2ee86f0f8e55d53301f75e963f07421a99a7ff4c0cad2c6a375c5ab1