Rust's never type finally lands after 10 years and 5 failed attempts

Rust 1.100

Rust 1.100.0 stabilizes the never type `!` after a decade and five failed attempts, letting it be named anywhere and making `Infallible` an alias for it. The release also ships the core `Allocator` API for custom allocators on `Vec` and `Box`, the `DropGuard` helper for running closures on every exit path, `conjure_zst` for safely creating zero-sized types, Cargo's unused-dependency warnings, and min-publish-age dependency cooldowns.