Rust

Improve comments more #4194

Job	Run time
cargo test (win64)	1h 16m 43s
cargo check	8m 42s
build with wasm-pack	2m 58s
Check License Header	2m 25s
Check cargo fmt	46s
cargo test (macos)	13m 58s
cargo test (macos-aarch64)	13m 48s
Verify MSRV (Min Supported Rust Version)	8m 45s
Verify Vendored Code	58s
cargo test (amd64)	12m 9s
cargo test datafusion-cli (amd64)	4m 30s
clippy	2m 20s
cargo doc	4m 15s
cargo test doc (amd64)	17m 18s
cargo examples (amd64)	14m 31s
Run sqllogictest with Postgres runner	4m 17s
cargo test pyarrow (amd64)	2m 55s
verify benchmark results (amd64)	14m 22s
check Cargo.toml formatting	2m 46s
check configs.md and ***_functions.md is up-to-date	3m 43s
cargo test hash collisions (amd64)	29m 18s
	4h 1m 27s

Provide feedback