Create What's New Entry for 16.1

What does this MR do and why?

This MR creates the what's new entry for the 16.1 release. I've added all of the primary features from the release post as the entries for What's New in 16.1.

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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