[TODO] Upgrade to npm 7

[ktmud]

https://github.blog/2021-02-02-npm-7-is-now-generally-available/

npm 7 is now generally available and your local npm may have been upgraded if you have auto-update turned on.

But it has some breaking changes, most notably the new lockfile format and how it handles peerDependencies. I did some testing and it seems the behavior for npm link has also changed---previously it will run npm install in linked packages, but now it doesn't (there is an open issue for this: npm/cli#2339)

Extra care is needed to update package-lock.json and package dependencies in superset-ui may have to be updated to accommodate the new peer dependency behavior.

Every committer MUST be notified to upgrade their local npm, too, when we do upgrade to npm 7, because of these breaking changes.

cc @rusackas @villebro @kgabryje @maloun96 @amitmiran137

[ktmud]

Looks like package-lock.json is inadvertently upgraded by #13079 .