Tracking issue for primitive module

[Mark-Simulacrum]

This tracks the core::primitive module.

There are no known blockers for stabilization, but there are some known bugs:

• docs are not linked rustdoc primitive re-export #67646

[Mark-Simulacrum]

It turns out that re-exports can't be feature gated so we're closing this out for now, but may reopen if we decide to pursue an alternative strategy.