feat(contrib/qxip): add contrib/qxip/hash package

[lmangani]

This PR adds contrib/qxip/hash package exposing basic go hashing functions to flux scripts.
Included readme explains the functionality.

This proposal might require adaptions and is very much intended for discussion and extension as core maintainers see fit.

Done checklist:

• Documentation
• Basic Tests

[sanderson]

@lmangani Looks great. Some minor doc suggestions, but that's it. Thanks!

[lmangani]

Thanks @sanderson for the review and for the doc corrections!
Just to be sure - is the cityhash source include method considered "proper" (as opposed to using the library) for inclusion in Fluxlib and as reference for future contribs with go code?

[wolffcm]

@lmangani Did you copy the code for CityHash instead of using the library for any particular reason? It would be preferable to import it in the normal way, with an import statement and an entry in go.mod.

[wolffcm]

I'd like to understand how/if we can import CityHash in the normal way.

[lmangani]

@lmangani Did you copy the code for CityHash instead of using the library for any particular reason? It would be preferable to import it in the normal way, with an import statement and an entry in go.mod.

Just following the contribution guidelines

A third-party package is defined as one that is not part of the standard Go distribution. Generally speaking, we prefer to minimize our use of third-party packages and avoid them unless absolutely necessarily. We'll often write a little bit of code rather than pull in a third-party package. To maximize the chance your change will be accepted, use only the standard libraries, or the third-party packages we have decided to use.

Edit: Generally speaking, it would make sense to import the library if it has any other applications present of future and think having cityhash64/128 in Flux would be quite useful on top of xxhash for high collision use cases, but since this is just a sideload contrib we had no such ambition. Curious to see what you guys think - Thanks for the time!

[wolffcm]

@lmangani This makes sense. Thanks for the rationale there. It's been a while since I've looked at the contribution guidelines.

[lmangani]

Thanks! Shall CityHash or any other hashing library become part of the Flux core, I'll update the code to use it/them.