chore(nimbus): move new ui into nimbus_ui_new

[jaredlockhart]

Because

• We're starting a new UI for Nimbus using Django Views/Forms/Templates
• Let's collect all the templates, static assets, views, tests in one folder so it's easier to collect and find things

This commit

• Moves all the new UI folders into nimbus_ui_new

fixes #10542

[mikewilli]

The idea is that this is a temporary folder until it reaches parity with nimbus_ui and then we rename that one? Or does this live potentially indefinitely alongside nimbus_ui? Thinking about things like the Results page that may not fit as neatly into HTMX and so might take a while to migrate, and how a longterm _new folder might start to look odd.

Also, heck yea :tada: /gif IT'S HAPPENING

[jaredlockhart]

@mikewilli Yeah after we reach parity in _new we can drop nimbus-ui and rename this one.