C++20 differences between emp::array and std::array

[emilydolson]

@mercere99 is probably already be aware of these, but just in case anyone else runs across them and is confused, I have come across a couple inconsistencies between emp::array and std::array that appear to crop up with c++20:

• The std::span constructor accepts an std::array directly whereas it only accepts an emp::array if you call .data() on it. Annoyingly, it does not appear to accept the result of calling .data() on an std::array.
• There appears to some subtle different behavior with iterator types that makes this method break with emp::array but not with std::array

[emilydolson]

Also this line breaks if arg_set_t is emp::array but works if it is std::array

(same problem happens in EventDrivenGP.hpp

[emilydolson]

This appears to be fixed!