Upgrade to Yarn Berry

[mehallhm]

Yarn classic (v1) entered maintenance mode in January of 2020. The recommendation is to upgrade to Yarn Berry (v4) . This process should not be terribly difficult from the repo side, but would require developer tooling updates.

As Yarn Berry operates through Corepack, there would be friction in this transition and Corepack is not certain to remain bundled with Node moving forward. There is not a major reason to move off of Yarn to alternative package managers, though that option does exist.