cp,hash: Move hash functions to its own package
For the upcoming katran support we need a 64 bits hash for IP addresses, SipHash is already suitable for that, so let's move the hash functions to its own package and provide Hash32 and Hash64 helpers
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For the upcoming katran support we need a 64 bits hash for IP addresses, SipHash is already suitable for that, so let's move the hash functions to its own package and provide Hash32 and Hash64 helpers