In dumper need overload to IE_TAG

[kaverdeka]

Add an operator() in the class dumper (printer.hpp) for IE_TAG that is used in print_all()

template <class IE>
constexpr void operator() (IE const& ie, IE_TAG) const noexcept {}

Example:

sink s;
diameter::slh::proto proto;
med2::print_all(s, proto); // error
..

//print all (named and not) IEs in full depth
template <class SINK, class IE, std::size_t MAX_LINE = 128>
void print_all(SINK&& sink, IE const& ie)

Compile error:

cannot convert 'med2::IE_TAG{}' (type 'med2::IE_TAG') to type 'med2::PRIMITIVE'
encoder(ie, IE_TAG{});