Make the trait level attributes uniform across all released crates in
the repo. Excludes things that are obviously not needed, eg, bench stuff
if there is not bench code.
- Remove `uninhabited_references` - this is allow by default now.
- Remove `unconditional_recursion` and mark the single false positive we
have with an `allow`.
Note, this does not add `missing_docs` to the `io` crate. There is an
open PR at the moment to add that along with the required docs.
ba1166a63b