[RFC] Standardize to Node 16 and NPM 8

[SamChou19815]

Summary

This PR standardizes our setup to use Node 16 and NPM 8, which enters active LTS recently. It's the first Node version that comes with NPM 8 (which doesn't change a lot for our purposes compared to NPM 7).

Reasons for this change:

• Node 16 enters active LTS, so it's stable enough. It's good to jump onto the latest version to enjoy new features.
• Some of our team members use the new M1 mac, which is only supported by Node 16+.
• Some of our team members might have already using NPM 7+, which it annoyingly prompts you to update by npm -i -g npm. It causes us to constantly remind them to revert package-lock.json changes.
• NPM 7+ has support for workspaces, which can better help us manage our codebases by splitting things into workspaces for better logically organization.

Notes

Everyone should download Node 16 from website once it's merged.

Test Plan

CI. Shouldn't have any user visible changes.

[dti-github-bot]

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