Use diagnostic items where possible
Clippy still uses a bunch of paths in places that could easily use already defined diagnostic items. This PR updates all references to such paths and also removes a bunch of them that are no longer needed after this cleanup.
Some paths are also used to construct new paths and can therefore not be removed that easily. I've added a doc comment to those instances that recommends the use of the diagnostic item where possible.
And that's it, cleaning crew signing off 🧹🗑️
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changelog: none
(only internal improvements)
cc: #5393
Fix the ICE 6539
Fixes#6539
It happened because `zero_sized_map_values` used `layout_of` with types from type aliases, which is essentially the same as the ICE 4968.
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changelog: Fix an ICE in `zero_sized_map_values`
This makes it possible to pass the `Impl` directly to functions, instead
of having to pass each of the many fields one at a time. It also
simplifies matches in many cases.
