Refactor e2e tests and fix a couple [ci e2e] [ci screenshots]

frontend/interfaces/webdriver.js

...tend/src/metabase/admin/people/components/GroupSelect.jsx

.../src/metabase/admin/people/components/UserGroupSelect.jsx

frontend/src/metabase/css/admin.css

frontend/test/e2e/admin/datamodel.spec.js

frontend/test/e2e/admin/people.spec.js

frontend/test/e2e/auth/login.spec.js

frontend/test/e2e/query_builder/query_builder.spec.js

frontend/test/e2e/query_builder/tutorial.spec.js

frontend/test/e2e/setup/signup.spec.js

frontend/test/e2e/support/backend.js

frontend/test/e2e/support/driver.js

frontend/test/e2e/support/jasmine.js

frontend/test/e2e/support/jasmine.json

frontend/test/e2e/support/sauce.js

frontend/test/e2e/support/setup.js

frontend/test/e2e/support/shared-resource.js

frontend/test/e2e/support/start-server.js

frontend/test/e2e/support/utils.js

frontend/test/e2e/support/webdriver.js