Move Sinsemilla primitive impl into `sinsemilla` crate #4051

Job	Run time
Test on i686-unknown-linux-gnu	22s
Test on ubuntu-latest	12s
Test on i686-unknown-linux-gnu with beta features	26s
Test on i686-unknown-linux-gnu with nightly features	25s
Book tests	15s
Code coverage	2m 27s
Intra-doc links	13s
Test on windows-latest	12s
Build target wasm32-unknown-unknown	13s
Build target wasm32-wasi	15s
Rustfmt	12s
Test on macOS-latest	15s
Bitrot check	13s
Test on ubuntu-latest with beta features	14s
Test on windows-latest with beta features	13s
Test on macOS-latest with beta features	15s
Test on ubuntu-latest with nightly features	12s
Test on windows-latest with nightly features	12s
Test on macOS-latest with nightly features	14s
	7m 0s

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