Move Poseidon primitive into `halo2_poseidon` #4065

Job	Run time
Bitrot check	1m 39s
Book tests	1m 29s
Build target wasm32-unknown-unknown	1m 50s
Build target wasm32-wasi	1m 44s
Code coverage	3m 37s
Intra-doc links	1m 32s
Test on ubuntu-latest	1m 55s
Test on i686-unknown-linux-gnu	13m 11s
Test on windows-latest	1m 54s
Test on i686-unknown-linux-gnu with beta features	14m 19s
Test on i686-unknown-linux-gnu with nightly features	15m 13s
Rustfmt	15s
Test on macOS-latest	10s
Test on ubuntu-latest with beta features	1m 56s
Test on windows-latest with beta features	1m 54s
Test on macOS-latest with beta features	1m 57s
Test on ubuntu-latest with nightly features	1m 57s
Test on windows-latest with nightly features	1m 54s
Test on macOS-latest with nightly features	1m 52s
	1h 10m 18s

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