Introduce return type for aggregate sum #20096

Job	Run time
cargo check	2m 31s
build with wasm-pack	3m 16s
cargo test (mac)	16m 9s
cargo test (win64)	23m 21s
Check cargo fmt	51s
Verify MSRV	11m 53s
Verify Vendored Code	1m 4s
cargo test datafusion-cli (amd64)	4m 25s
cargo examples (amd64)	9m 38s
clippy	4m 30s
check Cargo.toml formatting	1m 57s
cargo test hash collisions (amd64)	8m 30s
cargo doc	3m 12s
cargo test (amd64)	8m 51s
cargo test doc (amd64)	9m 15s
cargo test pyarrow (amd64)	2m 10s
verify benchmark results (amd64)	9m 33s
check configs.md is up-to-date	3m 24s
Run sqllogictest with Postgres runner	3m 4s
	2h 7m 34s

Provide feedback