Rust 1.100.0

Rust 1.100.0, released November 12, brings changes across the language, compiler, standard library, Cargo, and supported platforms. Language updates stabilize the never type and `extern "custom"`, add a lint for repeated representation attributes, and adjust several existing lints. The compiler stabilizes profile-guided optimization sample use and enables its next trait-solver implementation by default for orphan checks. Platform changes promote `wasm32-wasip3` to Tier 2, add a Tier 3 PlayStation 3 target, and change the status of the 32-bit Windows GNU target. The standard library stabilizes custom allocators and a broad set of allocator-aware APIs, alongside utilities such as `bool::toggle` and string and path prefix-trimming methods.

Cargo adds configurable lints, including a built-in check for unused dependencies, and supports dependency cooldowns that exclude recently published versions unless already recorded in the lockfile. `cargo install` now uses a packaged lockfile by default, while build-artifact directory layouts change and should not be treated as stable. Users should review compatibility changes: closures capture variables more precisely in some `if let` cases, the never-type fallback is now `!` across editions, and `Infallible` becomes an alias for that type. Other changes affect trait-object compatibility checks, ARM target-feature validation, x86 ABI behavior, Unicode handling, and iterator method selection. These may expose errors or require build adjustments, particularly for affected ARM targets.