Indicate Node.js supported versions

[legobeat]

PR description

• Add engines.node to indicate supported Node.js version range
  • Assuming minimum 16 since Update Ganache to 7.9.1; turn off Node 14 and turn on Node 20 (and fix a bad type) #6169 removed v14 from CI
• Add .nvmrc set to lts/*
• ci: Read version for yarncheck job from .nvmrc instead of using harcoded vesion

Testing instructions

Documentation

• I thought about documentation and added the doc-change-required label to this PR if documentation updates are required.

Breaking changes and new features

• I have added any needed breaking-change and new-feature labels for the appropriate packages.

[haltman-at]

Hm, do we want to set .nvmrc to lts/*? That's what it is now, but we've often lagged behind a bit.

[legobeat]

How about pinning to lts as of now, 18?

I guess it's mostly a matter of if you want future upgrades to be explicit or not.

[haltman-at]

Oh, well right now we're still supporting 16, so...?

[legobeat]

@haltman-at Note that the value in .nvmrc does not affect which version unit tests are being run in (which still includes 16) - only the yarncheck job is being changed to use .nvmrc here.

[gnidan]

This approach is probably what we should've been doing all along.

For that .nvmrc, I think we probably would want that yarncheck job to run on the earliest Node version we support, but it probably doesn't matter too much.

One approve from me :) Thank you!

[haltman-at]

Well, if Nick says it's good, then I'm also OK with it!