The utils::make_nested_exception_ptr function works similar to
std::throw_with_nested, but instead of storing the currently thrown
exception as the nested exception and then immediately throwing the new
exception, it receives the nested exception as an std::exception_ptr and
also returns an std::exception_ptr.
If the standard library supports it, the function does not perform any
throws. Otherwise the fallback logic performs two throws.
Introduces a utility function which allows obtaining a pointer to the
exception data held behind an std::exception_ptr if the data matches the
requested type. It can be used to implement manual but concise
try..catch chains.
The `try_catch` has the best performance when used with libstdc++ as it
uses the stdlib specific functions for simulating a try..catch without
having to actually throw. For other stdlibs, the implementation falls
back to a throw surrounded by an actual try..catch.
