adding expr to string for IsNotNull IsTrue IsFalse and IsUnkown #24849

Job	Run time
cargo check	9m 57s
build with wasm-pack	2m 14s
cargo test (macos)	23m 33s
cargo test (macos-aarch64)	11m 7s
Verify Vendored Code	1m 4s
cargo test (win64)	45m 53s
Check cargo fmt	43s
Verify MSRV (Min Supported Rust Version)	7m 14s
cargo test (amd64)	10m 15s
cargo examples (amd64)	10m 10s
check Cargo.toml formatting	3m 8s
clippy	6m 5s
cargo test hash collisions (amd64)	9m 50s
cargo doc	4m 9s
cargo test datafusion-cli (amd64)	3m 42s
cargo test doc (amd64)	12m 41s
Run sqllogictest with Postgres runner	3m 9s
cargo test pyarrow (amd64)	2m 36s
verify benchmark results (amd64)	9m 39s
check configs.md is up-to-date	2m 19s
	2h 59m 28s

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