Warn about unknown or renamed lints

Originally I tried to do a much broader refactoring that got rid of `init_lints` altogether. My reasoning is that now the lints aren't being run anymore (after https://github.com/rust-lang/rust/pull/73566), there's no need to ignore them explicitly. But it seems there are still some lints that aren't affected by setting `lint_mod` to a no-op:

```
deny(pub_use_of_private_extern_crate)
deny(const_err)
warn(unused_imports)
```

(there are possibly more, these are just the ones that failed in the rustdoc test suite).

Some of these seem like we really should be warning about, but that's a much larger change and I don't propose to make it here. So for the time being, this just adds the `unknown_lints` and `renamed_or_removed_lints` passes to the list of lints rustdoc warns about.

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