Update rust-toolchain to 2023-11-16 (#6492)
This updates the rust toolchain to 2023-11-16 and:
- Removes now-unnecessary `#![feature(async_fn_in_trait)]`
- Applies auto-fixable lint fixes
- Uses `Cargo.toml` new `lint` section instead of command line rustc
flags
Test Plan: Tested with updated Next.js in a create-next-app
Closes PACK-1978
