CI: Check .nvmrc versus package.json engines

[anomiex]

Changes proposed in this Pull Request:

Check that the node version in .nvmrc matches the version required by
.engines.node in package.json in CI.

Jetpack product discussion

Came up in passing in review of #19705.

Does this pull request change what data or activity we track or use?

No

Testing instructions:

• Is CI happy?
• Try changing the versions to not match. Is that caught?

[github-actions]

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