chore: Update to Rust 1.91.0 (#10885)
### Description
Rust devs forbid using let-chains for non-2024 edition code (or it's a
bug?) so `#![feature(let-chains)]` is ignored, and the code fails to
compile. refactored a few pieces in turborepo-lib so it uses older
behavior
the only clippy lint fixed is the Default deriving
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Co-authored-by: Anthony Shew <anthony.shew@vercel.com>
