[dev]: separate unit and end-to-end testing

> In the future, we should consider separating the tests. We could have test:unit and test:e2e and then have separate jobs for each in ci.

When #2643 gets merged, running `yarn test` will only work if you have `code-server` running. Not ideal. 

Instead, we should separate them and make it so both unit tests and e2e tests can be run locally and separately in ci. 