Rust

Add test to verify `count` aggregate function should not be nullable #31093

Job	Run time
Check cargo fmt	40s
cargo check	5m 40s
build with wasm-pack	3m 52s
cargo test (macos)	11m 24s
cargo test (macos-aarch64)	13m 5s
Verify Vendored Code	50s
cargo test (win64)	45m 57s
Verify MSRV (Min Supported Rust Version)	7m 0s
check configs.md is up-to-date	2m 57s
check Cargo.toml formatting	2m 56s
cargo test hash collisions (amd64)	14m 3s
clippy	6m 50s
cargo test (amd64)	10m 10s
cargo doc	4m 9s
cargo test datafusion-cli (amd64)	4m 14s
cargo test doc (amd64)	14m 49s
cargo examples (amd64)	13m 19s
Run sqllogictest with Postgres runner	3m 44s
cargo test pyarrow (amd64)	3m 1s
verify benchmark results (amd64)	12m 5s
	3h 0m 45s

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