Model R: allow for quick visual scan of all possible screens

[grdddj]

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Current UI tests dashboard is very good for examining a couple specific workflows - what we need right now for model R is one place to see all the unique screens to quickly see some outlier issues and to discuss overall design.

It would be nice to have a webpage similar to that index.html showing all the possible screens from the UI tests, possibly also with links to all the scenarios where this screen occurs.

My view locally (no webpage, just all unique screenshots in one directory):

[grdddj]

Done in 19e49d7

It is available as an artifact under artifacts/test_ui_report/all_unique_screens.html, in the same dir as already used index.html. Each image is also a link that leads to a list of all test-cases where this exact screen is appearing.

The second helper dashboard was created under artifacts/test_ui_report/all_screens.html to show all the test-cases at one place - to quickly scan multiple test-cases without need to open multiple tabs from index.html.

These two dashboards are actually connected - when clicking on any image from all_screens.html, it goes to all_unique_screens.html's section with that image and a list of occurrences. And vice-versa, from all_screens.html, links point to specific test-cases that contain a specific screen.

As a bonus, it works for T1 and TT as well.