Fix clippy warnings - #2

@copilot has the issues fixed in this all been resolved by other pull requests?

Closing as obsolete. The substantive Clippy fixes from this PR were independently incorporated in dddf0ab ("Package upgrade and clippy fixes"), including deriving Default for the JSON client and the conversion cleanups in dns.rs and io.rs. The remaining changes are formatting/import-order cleanup.\n\nCurrent main passes cargo clippy --workspace --all-targets -- -D warnings, and this historical patch no longer applies cleanly to any of its four files. Thank you for the contribution.