Docs for primitive type helper modules should stay in their lane

[camsteffen]

Summary of primitive types with corresponding std modules:

Primitive type	std module	std module docs first line
array	std::array	Helper functions and types for fixed-length arrays.
char	std::char	A character type.
slice	std::slice	A dynamically-sized view into a contiguous sequence, [T].
str	std::str	Unicode string slices.
pointer	std::ptr	Manually manage memory through raw pointers.
f32	std::f32	Constants specific to the f32 single-precision floating point type.
f64	std::f64	Constants specific to the f64 double-precision floating point type.

Some of the std modules' documentation sound like documentation for the primitive type itself. Others do not. The std::slice and slice docs almost look like they are supposed to be identical but there are some minor (perhaps accidental) differences. std::ptr has some unique content that may be better fit for the pointer docs.

In general, I think the std docs should be very brief and primarily work as a signpost pointing to the primitive type docs. But of course they should also document the module itself, without sounding like "I am char". Some more specific conventions could be established.

[slightlyoutofphase]

On a semi-related note, as I mentioned here it's IMO very confusing that on the page for pointer, the Primitive Type pointer methods list in fact includes all of *const T, *mut T, *const [T], and *mut [T], which leads to a large amount of duplicated method names in practice.