Make data-test attribute mandatory

[Sodik]

Not all components have data-test attribute. It breaks existing e2e and blocks creating new reliable test cases

[utkukaratas]

what's worse is css-modules name mangling does make it very hard to deal with the components.

for example to get the text of a button you need selectors like this: $("[data-test='user-menu-button-trigger'] div[class*='__truncatedText'] span").text()

can't think of a simple solution :/