refactor: add `get_available_parallelism` function #35455

Job	Run time
Check License Header	2m 16s
cargo check	7m 19s
build with wasm-pack	3m 5s
cargo test (win64)	1h 14m 54s
Check cargo fmt	36s
cargo test (macos)	14m 17s
cargo test (macos-aarch64)	13m 12s
Verify Vendored Code	44s
Verify MSRV (Min Supported Rust Version)	9m 11s
cargo examples (amd64)	14m 24s
cargo test datafusion-cli (amd64)	4m 32s
cargo doc	4m 31s
cargo test (amd64)	11m 44s
Run sqllogictest with Postgres runner	4m 18s
cargo test pyarrow (amd64)	3m 4s
verify benchmark results (amd64)	13m 43s
check Cargo.toml formatting	2m 42s
clippy	7m 26s
check configs.md and ***_functions.md is up-to-date	3m 48s
cargo test hash collisions (amd64)	27m 48s
cargo test doc (amd64)	17m 21s
	4h 0m 55s

Provide feedback