Rust

add downcast_delegate #626

Job	Run time
Verify Vendored Code	1m 7s
linux build test	7m 5s
cargo test (macos-aarch64)	7m 53s
Check cargo fmt	1m 6s
build and run with wasm-pack	4m 53s
Verify MSRV (Min Supported Rust Version)	5m 59s
cargo test (amd64)	15m 13s
cargo check datafusion-common features	2m 6s
check Cargo.toml formatting	3m 28s
cargo check datafusion-functions features	2m 52s
check example README is up-to-date	5m 33s
cargo check datafusion-proto features	5m 11s
cargo test datafusion-cli (amd64)	5m 17s
cargo check datafusion features	11m 14s
check configs.md and ***_functions.md is up-to-date	6m 21s
cargo examples (amd64)	15m 40s
verify benchmark results (amd64)	13m 37s
clippy	7m 39s
cargo test doc (amd64)	9m 27s
Run sqllogictest with Postgres runner	7m 3s
Run sqllogictest in Substrait round-trip mode	6m 58s
cargo check datafusion-substrait features	11m 4s
cargo doc	6m 1s
	2h 42m 47s

Provide feedback