Tracking issue for SipHash13/SipHash24

[alexcrichton]

Added in #33940, these two structs which implement Hasher live in the std::hash module. This issue will track their stabilization, and some open questions when we added them were:

• Do we want to export any more hasher implementations? Right now SipHasher is stable, but perhaps we don't want to expand?
• If we do stabilize, what to do about the SipHasher name?

[sfackler]

The libs team discussed these types, and are placing them into final comment period to deprecate SipHasher, SipHash13, and SipHash24, and then remove SipHash13 and SipHash24 in a future release.

While RandomState is currently implemented with SipHash-1-3, this will not necessarily continue to be the case in the future if, for example, a faster cryptographic hash is developed or security flaws are found in it. We don't want to be forced to keep these implementations around forever if that happens.

That being said, we are interested in moving forward on standard library support for faster hash maps and sets for small keys like integers where HashDoS is not a concern. This would most likely involve the addition of a FastHasher backed by something like FNV, and possibly FashHashMap and FastHashSet type definitions.

[alexcrichton]

The libs team discussed this during triage yesterday and the conclusion was to deprecate