Use `std::source_location::function_name()` for getting the name of a type in C++20 mode

[n0F4x]

I recently noticed that you can use std::source_location::function_name() for getting the name of a type.
I didn't test it.
Reference: https://github.com/qlibs/reflect/

This is a more standard way of acquiring a type_name.
Just wanted to put this out here.

[skypjack]

It's a C++20 way to do that, while EnTT is still on C++17. It should move to C++20 after the next release though.
Just keep the issue around until then, and experiment with the new function when it's done. 👍