Find crate by name should return a vector

[celinval]

Since a crate name can match more than one crate, I was wondering if we should return a vector instead of an Option<Crate>.

See an example on rustc test tests/codegen/nounwind.rs.

[spastorino]

I think this can be closed after rust-lang/rust#116543 from @ouz-a, right?.

[ouz-a]

Yeah