C++26: More function wrappers

C++26 continues to fill the gaps in our type-erased callable wrapper story. We already had std::function since C++11 and std::move_only_function since C++23, but there were still missing pieces. Now we’re getting two new additions: std::copyable_function and std::function_ref. What’s wrong with std::function? std::function has served us well, but it has two well-known issues. First, it can ...