Refactor tests for union sorting properties, add tests for unions and constants #32906

Job	Run time
Check cargo fmt	40s
cargo check	10m 39s
build with wasm-pack	2m 38s
cargo test (macos)	11m 48s
cargo test (macos-aarch64)	10m 56s
Verify Vendored Code	48s
cargo test (win64)	56m 13s
Verify MSRV (Min Supported Rust Version)	7m 16s
cargo test datafusion-cli (amd64)	4m 12s
cargo test (amd64)	10m 21s
clippy	5m 44s
cargo test hash collisions (amd64)	14m 46s
cargo test doc (amd64)	15m 50s
cargo doc	4m 36s
cargo examples (amd64)	13m 44s
Run sqllogictest with Postgres runner	3m 32s
cargo test pyarrow (amd64)	3m 1s
verify benchmark results (amd64)	12m 38s
check Cargo.toml formatting	3m 0s
check configs.md is up-to-date	3m 0s
	3h 15m 22s

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