Rust

add downcast_delegate #628

Job	Run time
Verify MSRV (Min Supported Rust Version)	4m 32s
build and run with wasm-pack	4m 9s
Verify Vendored Code	1m 29s
Check cargo fmt	1m 10s
linux build test	4m 34s
cargo test (macos-aarch64)	4m 53s
Run sqllogictest with Postgres runner	1s
cargo check datafusion-common features	1s
cargo check datafusion-proto features	1s
cargo check datafusion features	1s
cargo check datafusion-functions features	1s
cargo test doc (amd64)	1s
clippy	1s
cargo check datafusion-substrait features	1s
cargo test datafusion-cli (amd64)	1s
check configs.md and ***_functions.md is up-to-date	1s
cargo test (amd64)	1s
Run sqllogictest in Substrait round-trip mode	1s
cargo examples (amd64)	1s
verify benchmark results (amd64)	1s
check example README is up-to-date	1s
cargo doc	1s
check Cargo.toml formatting	1s
	21m 4s

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