[rustdoc] Primitive types don't appear in search

[Seeker14491]

Most primitive types don't appear in the search results. Instead, only the module appears, such as std::str. The primitive type bool does appear though, as there is no std::bool. So it looks to me like these are mistakenly being treated as duplicates and not shown. This is a regression from stable.

Stable:

Nightly:

cc @GuillaumeGomez