Fixes#9182
Now we are careful when to handle events - before or after updating intersected set.
Added general E2E and detailed unit tests for selecting.
Also discovered, that sometimes the test are running while nodes are not yet in right positions. Added an instruction ensuring the position is right.
- Closes#8179
# Important Notes
- ⚠️ These tests are currently *not run* on any CI workflow.
- There is some unused code for mocking the PM. This has been intentionally kept, as this may be useful in the future.
Note that this may be useful for testing the dashboard, however the dashboard is currently only tested in cloud mode
- that is, without the backend switcher, and with only the remote backend available. As such, currently it uses HTTP API mocks, and no PM mock.