Convenience const fn for Margin, Rounding and Shadow #9568

Job	Run time
android	22s
Check wasm32 + wasm-bindgen	2m 54s
cargo-deny aarch64-apple-darwin	38s
Format + check + test	6m 2s
cargo-deny aarch64-linux-android	40s
Check Windows	1m 43s
cargo-deny i686-pc-windows-gnu	39s
cargo-deny i686-pc-windows-msvc	38s
cargo-deny i686-unknown-linux-gnu	38s
cargo-deny wasm32-unknown-unknown	42s
cargo-deny x86_64-apple-darwin	39s
cargo-deny x86_64-pc-windows-gnu	43s
cargo-deny x86_64-pc-windows-msvc	42s
cargo-deny x86_64-unknown-linux-gnu	39s
cargo-deny x86_64-unknown-linux-musl	41s
cargo-deny x86_64-unknown-redox	41s
	19m 1s

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