Add rendezvous hash URI scorer

[advayakrishna]

Before this PR

Adds a new URI scoring mechanism based on rendezvous hashing:
https://en.wikipedia.org/wiki/Rendezvous_hashing

At initialization, clients can specify a header value used to generate an ordering on the URIs - this means that clients can take advantage of server-side read or write locality by sending requests for identical keys to the same URI in the average case. If there are n URIs and one changes, in expectation 1/n requests would be sent to a different node. It is important that clients do not rely on this routing behavior for correctness as requests may be retried at any of the URIs in the case of errors.

After this PR

==COMMIT_MSG==
Add rendezvous hash URI scorer to deterministically balance requests across URIs
==COMMIT_MSG==

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Description

Add rendezvous hash URI scorer to deterministically balance requests across URIs

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