Rust

Minor: consolidate ConfigExtension example into API docs #4244

Job	Run time
Check License Header	2m 13s
Check cargo fmt	41s
linux build test	3m 58s
build with wasm-pack	3m 16s
cargo test (macos-aarch64)	14m 14s
Verify MSRV (Min Supported Rust Version)	9m 37s
Verify Vendored Code	55s
cargo check datafusion	4m 46s
cargo check no default features	7m 42s
cargo doc	4m 43s
cargo check functions	1m 38s
cargo test (amd64)	13m 31s
cargo test datafusion-cli (amd64)	4m 49s
cargo test doc (amd64)	17m 44s
cargo examples (amd64)	15m 7s
verify benchmark results (amd64)	8m 10s
check Cargo.toml formatting	3m 1s
clippy	1m 50s
check configs.md and ***_functions.md is up-to-date	3m 44s
cargo test hash collisions (amd64)	17m 47s
Run sqllogictest with Postgres runner	4m 20s
cargo test pyarrow (amd64)	3m 0s
	2h 26m 46s

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