upgrade to yarn v2

[joshgummersall]

See Migration Guide. We would not be using Zero installs (.gitignore implications, see here for details)

In particular, we may need to:

• Stop listing "shared dependencies" in the root package.json file, as hoisting is now strongly discouraged
• Use --immutable instead of --frozen-lockfile
• Rewrite lifecycle scripts that use pre/post (see here for more details
• Possibly fix ADO pipelines that use .npmrc (see here, in particular we should aim to use environment variables)
• Use yarn dlx instead of npx
• Possibly use yarn node instead of node
• Leverage workspace: style versioning