Epic: Resolve v6 -> v7 regressions

[lukekarrys]

In the RFC meeting on 2021-09-22 we discussed tracking/fixing regressions from npm6, and fixing those before npm8.

This is a (so far incomplete) list of those regressions I've found:

• [BUG] npx package@version uses incorrect installed version in npx 7 cli#3210
• [BUG] NPM 7.x broke the "--json" CLI parameter cli#2740
• [BUG] npx failed: Cannot read property 'spec' of undefined cli#3021

[ljharb]

We discussed trying to fix them in npm 7, specifically, to ease the upgrade path - ideally they wouldn't have to wait til npm 8.

There's also

• [BUG] NPM v7 private registry authentication 401 (v6 works) cli#2508
• [BUG] NPM v7 uses SSH instead of an explicit HTTPS for GitHub repos cli#2610
• possibly [BUG] Cannot read property 'spec' of undefined when using npm install --prefix + tmpdir on mac  cli#3256
• possibly [BUG] Downgrading to previous npm version deletes all global packages. cli#3671

[wraithgar]

• [BUG] When using non-npm registry, scoped resolved URLs are being rewritten cli#3530
• [BUG] npm update -g package@latest removes all global packages cli#3175

[wraithgar]

• [BUG] package.json#/config/*: Array changed behaviour to joining items with double new-line cli#3775

[wraithgar]

• [BUG] package.json has "lockfileVersion": 2 but is missing "hasInstallScript": true cli#2606

[lukekarrys]

• [BUG] --parseable has no effect on audit cli#3863