Split npm from node package

[davepwsmith]

This would allow both node and npm to be kept properly up to date using just brew. node could depend on npm. I have no real knowledge of what this would break or how difficult it would be, so it's just a suggestion and I won't be offended if it's summarily dismissed!

[DomT4]

Not going to happen, I'm afraid. We did this previously and it ended up breaking both Node & npm pretty regularly, and the end result was that Node/npm to this day are hesitant to tell people to use brew to install the software (We've fixed those problems, but the perception remains).

Various discussions in #3762, #22408, #27479, #28075.