Upgrade Zola Ember (3.28) & Node 16

[allthesignals]

Closes #1098

This PR references an upcoming shared addon, labs-shared, that combines all the various components into a single addon to simplify upgrades:

https://github.com/NYCPlanning/labs-zola/issues/1098#issuecomment-1453941121

More, this PR upgrades Ember to the latest (3.28) and Node (16).

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[TylerMatteo]

@allthesignals this looks just about ready to send to QA but I'd like to switch it over to our fork of labs-shared first. See my PR here for details. Thanks for the fast progress on this round of upgrades!

[allthesignals]

Thanks, I'll get to this this weekend.