Refactor E2E tests to run outside of project

[philprime]

If we run the E2E tests using yarn test:e2e, most of the tests are run in the current project. While this is convenient for manual testing and analysis, it pollutes the git status and it can lead to committing e2e generated files. Furthermore, re-running tests with changes from previous runs results in tests not being deterministic.

Instead I propose that e2e test applications are copied to temporary directories, which are then used as working directories for the tests.

This should lead to yarn test:e2e leaving the checked out project untouched.

We might have to look into coverage directories being at the correct position for pushing to Codecov