yari chore(deps)!: migrate from yarn to npm + workspaces

Experimental PR to see how easy a switch back to npm would go.

~~⚠️ This PR is blocked by [this error.](https://github.com/mdn/yari/pull/6322#issuecomment-1133227129):~~

``` Error: 17:56:38 Error: Cannot find module 'cookie' Require stack: - /home/runner/work/yari/yari/libs/get-locale/index.js - /home/runner/work/yari/yari/deployer/aws-lambda/content-origin-request/index.js - /home/runner/work/yari/yari/deployer/aws-lambda/tests/server.js ```

~~To update this PR:~~

Run git rebase -i upstream/main
Choose edit for the first two commits.
Run git ls-files package-lock.json '**/package-lock.json' | xargs -n 1 dirname | xargs -n 1 -I % sh -c 'pushd %; rm -rf node_modules package-lock.json yarn.lock; npm install; popd'
Run git commit --amend --date=now
Run git rebase --continue

May 20 '22 07:05 caugner

This pull request has merge conflicts that must be resolved before we can merge this.

May 20 '22 12:05 github-actions[bot]

I have no clue what causes this error:

Error:  17:56:38 Error: Cannot find module 'cookie'
Require stack:
- /home/runner/work/yari/yari/libs/get-locale/index.js
- /home/runner/work/yari/yari/deployer/aws-lambda/content-origin-request/index.js
- /home/runner/work/yari/yari/deployer/aws-lambda/tests/server.js
____STDERR____
Error: Cannot find module 'cookie'
Require stack:
- /home/runner/work/yari/yari/libs/get-locale/index.js
- /home/runner/work/yari/yari/deployer/aws-lambda/content-origin-request/index.js
- /home/runner/work/yari/yari/deployer/aws-lambda/tests/server.js
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at Object.<anonymous> (/home/runner/work/yari/yari/libs/get-locale/index.js:1:19)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Object.nodeDevHook [as .js] (/home/runner/work/yari/yari/deployer/aws-lambda/tests/node_modules/node-dev/lib/hook.js:60:7)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)

(I even tried to add cookie everywhere, and it had no effect.)

May 20 '22 19:05 caugner

This pull request has merge conflicts that must be resolved before we can merge this.

May 23 '22 11:05 github-actions[bot]

This pull request has merge conflicts that must be resolved before we can merge this.

May 23 '22 23:05 github-actions[bot]