refactor(clippy): Reduce some Clippy warnings

[linyihai]

What this PR want to do

Tried to complete #3802 as well as possible.

This PR wants to reduce some Clippy warnings that worth fixing. Almost all of the changes are based on clippy prompts. And passed the MSRV 1.63 test.

Some of the warnings have not changed, mainly based on Clippy's false positives, and some clippy rules are newer than the current MSRV 1.63.

How to test and review

Needs downgrade some crate versions to run on MSRV 1.63.

cargo update tokio --precise 1.38.1 
cargo update tokio-util --precise 0.7.11
cargo update hashbrown --precise 0.15.0
cargo update regex --precise 1.9.6
cargo update async-stream --precise 0.3.5
cargo update tokio-stream --precise 0.1.15

Run cargo +1.63-x86_64-unknown-linux-gnu clippy --workspace --no-deps --all-targets --features="full" -- -D warnings
The warnings/error reduces to 7.

[seanmonstar]

Thanks, several of these are fine changes. I commented inline on the ones I think clippy is wrong about.

[seanmonstar]

Perfect, good work, thank you!