port flatten to datafusion-function-array #24207

Job	Run time
cargo check	3m 14s
Check cargo fmt	37s
cargo test (macos)	17m 57s
build with wasm-pack	2m 28s
cargo test (macos-aarch64)	11m 59s
Verify MSRV (Min Supported Rust Version)	7m 7s
Verify Vendored Code	55s
cargo test (win64)	43m 4s
cargo test (amd64)	10m 7s
cargo test datafusion-cli (amd64)	3m 41s
clippy	6m 24s
cargo doc	3m 40s
cargo test hash collisions (amd64)	10m 3s
cargo test doc (amd64)	12m 55s
cargo examples (amd64)	10m 41s
Run sqllogictest with Postgres runner	3m 15s
cargo test pyarrow (amd64)	2m 51s
verify benchmark results (amd64)	10m 27s
check Cargo.toml formatting	2m 59s
check configs.md is up-to-date	2m 35s
	2h 46m 59s

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