Convert approx_distinct to UDAF #27769

Job	Run time
cargo check	3m 30s
Check cargo fmt	39s
build with wasm-pack	2m 22s
cargo test (macos)	19m 17s
cargo test (macos-aarch64)	9m 49s
Verify Vendored Code	55s
cargo test (win64)	35m 58s
Verify MSRV (Min Supported Rust Version)	6m 45s
cargo examples (amd64)	12m 10s
cargo test (amd64)	9m 31s
cargo test datafusion-cli (amd64)	3m 57s
cargo doc	3m 35s
cargo test doc (amd64)	13m 8s
Run sqllogictest with Postgres runner	3m 30s
clippy	4m 59s
cargo test hash collisions (amd64)	8m 52s
cargo test pyarrow (amd64)	2m 57s
verify benchmark results (amd64)	11m 0s
check Cargo.toml formatting	2m 59s
check configs.md is up-to-date	2m 29s
	2h 38m 22s

Provide feedback