No documentation for primitives in `core`

[rossmacarthur]

There is no documentation for primitives in core, the only documentation exists in std. I don't think there is any reason for a user to assume that all associated functions and methods on primitive types that are available in std are also available in core.

Some confusing things:

• The primitives are not listed in the crate root. See here
• The core::primitive module documentation primitives have no links. See here
• The the primitive types modules such as core::i32 link to the std documentation for primitives. See here

[rossmacarthur]

@rustbot modify labels: +C-enhancement +T-doc +T-rustdoc +A-rustdoc-ui

[jyn514]

Duplicate of #73423. See also #62909.