e2e tests: remove protractor, decide next steps

When Stork's angular project was created a long time ago (in 2020), it added the default end-2-end tests with protractor. AFAICT this was never used. The protractor tool has reached EOL in Aug 2023. We should clean up this outdated mess and...

• get rid of Protractor (and likely all of the default files in webui/e2e)
• decide if we want to develop end 2 end tests
  • if the answer is yes, evaluate alternatives
  • add a few e2e tests using new testing framework

As for now, the five leading alternatives seem to be Nightwatch.js (11.5k), Cypress (45.2k), Playwright (56.6k), TestCafe (9.7k), WebDriverIO (8.4k). The number in brackets show number of stars on github, which is some indicator of popularity. Other aspects to consider: some frameworks use Selenium (which @wlodek had bad experiences with). Playwright is developed by Microsoft, which might be a factor. The link above contains example test cases.