Flattened view with subtests results

[Orphis]

When making queries, we can easily visualise the high level list of tests that are passing or failing (for example here). But in a scenario where we are interested in the failures, we still need to click on each and every test case to show what are the matching subtests.

A flat view with those listed would be really useful, way more than listing many tests that are failing at 0/1, requiring a click and a page load.

[foolip]

Flattening of results is something that would be useful for Interop 2022/23 as well. In those contexts, I think flattening to tests (not subtests) would be better, but it's a very similar feature.

There's already something like this implemented in some corner of wpt.fyi, I think when comparing PR results. I can't find the code for it in a quick search though.