chore: reduce clippy allowances

[vincent-thomas]

Summary

• replace a broad clippy allow in api::ops with the simpler Option::and form
• simplify remove_dir_all state advancement to avoid the never_loop allow
• replace datagram test type-complexity allows with local type aliases

Test Plan

• cargo fmt --check
• RUSTFLAGS=-Dwarnings cargo clippy --workspace --all-targets --all-features
• cargo test -p lio --all-features --test net_udp --test net_socket_datagram --test fs_remove_dir