CNDB-15469: Add NVQunatization::create method that takes global mean

[michaeljmarshall]

In some applications, it will be better to compute the global mean iteratively at the time of insertion into the graph instead of when creating the NVQuantization object. Therefore, I propose adding a new create method that takes an already computed scaled global mean vector.

Because we update the existing compute method to call this new create method, the existing tests fully cover the new method.

This work is part of https://github.com/riptano/cndb/issues/15469.

[github-actions]

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[marianotepper]

LGTM

[jshook]

LGTM