Yarn berry

[mehallhm]

Purpose

Migrates off of the end-of-life Yarn Classic to the actively maintained Yarn Berry version. In general, it is a drop in replacement, using the Node experimental Corepack as the preferred installation / management tool (the irony of managing a package manager).

Tickets

Closes #225, Closes #232

Feature List

• Switches from Yarn Classic to Yarn Berry in node_modules compatibility mode.
• Updates the Dockerfile to enable Corepack and use the same version of Yarn as dev, ensuring consistency.
• Prepped Dockerfile for a better build system in the future. Yarn Berry forces us to stop abusing Yarn like we were before so some of this needed to happen now anyway. This will be something that will show its value soon...
• Updates the GH actions to use Corepack to install deps (and generally get them to newer versions).

Notes

I will open a PR on searchneu soon to ensure that there is a version locked in because Corepack likes to add itself otherwise.

Reviewers

Primary:
@ananyaspatil

Secondary:
@Anzhuo-W @nickpfeiffer05 @cherman23

[coveralls]

coverage: 80.173%. remained the same
when pulling 3adf0c3 on yarn-berry
into a5d14a0 on master.

[mehallhm]

I'm really not liking these request unit tests... They are super finicky both in CI and locally. I can barely curl these URLs! Something we should improve....