Rust

Use `u8` in `Rounding`, and introduce `Roundingf` #13894

Job	Run time
android	22s
cargo-deny aarch64-apple-darwin	37s
Check wasm32 + wasm-bindgen	2m 19s
cargo-deny aarch64-linux-android	37s
cargo-deny i686-pc-windows-gnu	38s
cargo-deny i686-pc-windows-msvc	37s
Check wasm32+atomics	1m 19s
cargo-deny i686-unknown-linux-gnu	37s
cargo-deny wasm32-unknown-unknown	39s
Format + check + test	2m 21s
cargo-deny x86_64-apple-darwin	36s
cargo-deny x86_64-pc-windows-gnu	41s
ios	20s
cargo-deny x86_64-pc-windows-msvc	39s
cargo-deny x86_64-unknown-linux-gnu	36s
cargo-deny x86_64-unknown-linux-musl	36s
cargo-deny x86_64-unknown-redox	36s
Run tests	2m 11s
Check Windows	1m 41s
	18m 2s

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