Warnings when compiling on windows: stdext::unchecked_array_iterator, and related factory functions are non-Standard extensions and will be removed in the future

[alexander-riss]

warning C4996: 'stdext::checked_array_iterator<T *>': warning STL4043: stdext::checked_array_iterator, stdext::unchecked_array_iterator, and related factory functions are non-Standard extensions and will be removed in the future. std::span (since C++20) and gsl::span can be used instead. You can define _SILENCE_STDEXT_ARR_ITERS_DEPRECATION_WARNING or _SILENCE_ALL_MS_EXT_DEPRECATION_WARNINGS to suppress this warning.

Would probably make sense to add a gsl::span switch for windows while min cpp version is still below cpp20?

[vitaut]

Looks like a duplicate of #3540.