35d6d70a64
rustc_metadata: Encode/decode some `LazyArrays` without an `Option` and a couple of related changes, see individual commits. Addresses comments in https://github.com/rust-lang/rust/pull/107166#discussion_r1083417124 and https://github.com/rust-lang/rust/pull/107166#discussion_r1083768417, cc `@cjgillot` `@oli-obk.`