This change uses the same "exact" paths as trait implementors
and type alias inlining to track items with multiple
reachable paths. This way, if you search for `vec`, you get
only the `std` exports of it, and not the one from `alloc`.
It still includes all the items in the search index so that
you can search for them by all available paths. For example,
try `core::option` and `std::option`, and notice that the
results page doesn't show duplicates, but still shows all
the items in their respective crates.
