Improve speed of `median` by implementing special `GroupsAccumulator` #35693

Job	Run time
Check License Header	2m 17s
cargo check	8m 18s
build with wasm-pack	3m 13s
cargo test (macos)	8m 44s
cargo test (macos-aarch64)	8m 19s
Verify Vendored Code	50s
cargo test (win64)	1h 10m 38s
Check cargo fmt	44s
Verify MSRV (Min Supported Rust Version)	8m 51s
cargo examples (amd64)	14m 30s
cargo doc	4m 25s
cargo test datafusion-cli (amd64)	4m 41s
cargo test (amd64)	12m 23s
Run sqllogictest with Postgres runner	4m 2s
cargo test pyarrow (amd64)	2m 59s
verify benchmark results (amd64)	14m 30s
check Cargo.toml formatting	2m 52s
clippy	2m 21s
check configs.md and ***_functions.md is up-to-date	3m 35s
cargo test hash collisions (amd64)	28m 20s
cargo test doc (amd64)	17m 25s
	3h 43m 57s

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