When running e2e tests, prevent needing to restart the app for every single test

[MattLish]

Currently, e2e tests require the entire app to be restarted between test runs.

This is because all the startup commands are run when starting the main process. Without re-running this startup process, the app cannot have the context reset between tests.

Requirements:

• Move startup commands to happen as part of the renderer process so resetting the window reruns them.
• Add a reset command between each test to reset the context by removing user preferences, modpack settings, etc.
• Move all the startTestApp to beforeEach instead of beforeAll