CI: Test that should complete correctly fail

## BUG

### Description
Some tests defined in Flint.test fail when they should complete correctly. The failure points always display `EDT Failure` which contains the asynchronous calls. We added await functions so the asynchronous calls should complete correctly and wait. This improved the succes rate but didn't completely resolve the issue.

### Workaround
Inside the CI there exists the option to rerun failed tests. Rerunning failed tests affected by this bug makes the test pass correctly.

### Resources
[test-results-ubuntu-20.04.zip](https://github.com/discipl/flinteditor-mps/files/9251873/test-results-ubuntu-20.04.zip)

Start with the failing tests described in Flint.test and inspect the attached test-results-ubuntu-20.04.zip for the repeated EDT Failure. Reproduce the failure in CI, compare first runs with reruns, and trace the asynchronous calls. Done means the affected tests complete reliably without requiring a rerun.

Written by the indexing model from the issue text.