`product_base` needs to record `std::type_info`

[pcanal]

product_base currently records and returns only the std::type_index of the underlying data. However one can not recover the std::type_info from the std::type_index (only the reverse is currently supported by C++).

In order for the I/O to know which type is being used, passing the std::type_info is much more convenient (one can demangle the name of the type info to get the C++ spelling of the type and ROOT records/remember the type_info).

Alternatively the I/O would have to be passed a map<std::type_index, ....> to understand the type_index (and/or ROOT dictionary would have to be enhanced to also record the type_index).