Add support for new Node.js builds for Apple silicon

[shadowspawn]

Pull Request

Problem

Node.js is available natively on Apple silicon from v16, but not before.

n is currently switching the architecture from arm64 to x64 on Darwin to allow installing older versions to run using Rosetta.

Related: #641

Solution

On Macs with Apple silicon...

• version resolution and remote listing include both the x64 and arm64 targets
• downloads for Node.js 16 and higher use arm64
• downloads for Node.js below 16 use x64
• specifying an explicit architecture using --arch shows and downloads only the matching architecture

I considered switching architecture if arm64 download missing, but decided simpler code and story switching based on the Node.js version.

ChangeLog

• on Macs with Apple silicon, use native arm64 for Node.js versions for version 16 and higher

[shadowspawn]

This PR assumes index.tab lists the arm64 as an available download, which isn't happening quite yet.

See nodejs/nodejs-dist-indexer#14