doc-gen: migrate scalar functions (other, conditional, and struct) documentation #36939

Job	Run time
Check License Header	2m 20s
linux build test	4m 51s
build with wasm-pack	3m 58s
cargo test (macos-aarch64)	14m 2s
Check cargo fmt	42s
Verify MSRV (Min Supported Rust Version)	10m 23s
Verify Vendored Code	50s
cargo check no default features	9m 58s
cargo check datafusion	5m 38s
cargo check functions	2m 23s
cargo test (amd64)	13m 45s
cargo test datafusion-cli (amd64)	5m 56s
cargo test doc (amd64)	19m 27s
cargo doc	6m 24s
cargo examples (amd64)	16m 25s
check Cargo.toml formatting	3m 37s
clippy	8m 10s
check configs.md and ***_functions.md is up-to-date	4m 47s
Run sqllogictest with Postgres runner	5m 35s
cargo test pyarrow (amd64)	3m 37s
verify benchmark results (amd64)	9m 34s
	2h 32m 22s

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