Change `unsafe_op_in_unsafe_fn` to be `warn`-by-default from edition 2024 This was previously FCPed: https://github.com/rust-lang/rust/issues/71668#issuecomment-1189396886 There were two blocking requirements: * Fix the `unused_unsafe` lint, done in https://github.com/rust-lang/rust/pull/100081 * Have `cargo fix` able to fix the lint, done in https://github.com/rust-lang/rust/pull/112017