Set Yarn version to v4

[cameronvoell]

Is your feature request related to a problem?

Though everything seems to be working with Yarn v1 currently, that Yarn version is not future-proof and will slowly get more outdated over time. According to Yarn docs, v4 is more stable, has new useful features and is much more performant: https://yarnpkg.com/getting-started/qa#why-is-the-yarn-package-on-npm-still-on-1x

Describe the solution to the problem

See migration steps here: https://yarnpkg.com/migration/guide

Describe the uses cases for the feature

No response

Additional details

Noted by @rygine in this PR:

v1 has been in maintenance mode since 1/2020. latest version now is 4.0.2, which requires corepack to be enabled.
just need to run corepack enable, then yarn set version stable. be sure to update the nodeLinker setting to node-modules to disable PnP mode.
that should hopefully just work. there are some GH actions updates as well. happy to sync on this if you'd like.