Fix #737, with random_init of distribution_safe_integral

[JAuriac]

From #735.
For exactly the integer types std::uniform_int_distribution permits, as its IntType parameter (short, int, long, long long, and unsigned variants). bool and char-like types are intentionally excluded as uniform_int_distribution is undefined behavior for those, and this file doesn't provide an alternative for them. A struct containing a bool or char member will fail to compile here rather than compile into a runtime undefined behavior.
To handle bool and char, the following would be needed :

// bool
static inline void random_init(std::uniform_random_bit_generator auto& gen, std::same_as<bool> auto& t)
{
	t = std::bernoulli_distribution(0.5)(gen);
}

// char
static inline void random_init(std::uniform_random_bit_generator auto& gen, narrow_integral auto& t)
{
	using T = std::remove_reference_t<decltype(t)>;
	using Wide = std::conditional_t<std::is_signed_v<T>, int, unsigned int>;
	t = static_cast<T>(std::uniform_int_distribution<Wide>(std::numeric_limits<T>::min(), std::numeric_limits<T>::max())(gen));
}

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[Yushan-Wang]

So, in the end, did this PR fix random_init for char and bool?
I saw the proposed solution in the PR's description, but not in the changes

[Yushan-Wang]

I wouldn't consider this a fix, since char and bool are only excluded, not fixed.

[jbigot]

The standard uses IntType with a comment about undefined behavior. This feels like we're trying to be a bit more Catholic than the Pope, here, but why not.

[jbigot]

The CHANGELOG entry can likely be polished a bit more. Focus on explaining the changes from a user point of view as described in the new CONTRIBUTING.md. What it changes for a user, not what you changed.

But overall, I'd say this can be merged from my point of view.

[jbigot]

good job