How do we break less tests when upgrading EUI in Kibana?

[JasonStoltz]

When we upgrade EUI in Kibana, it tends to break a lot of tests. Primarily as a result of tests either targeting our components with selectors other than data-test-subj, or more commonly, snapshot tests that include EUI components. How do we make this easier?

[walterra]

FWIW, the ML team started an effort to migrate away from enzyme and get rid of snapshots along the way, we'll try to use @testing-library in the future only and not rely on implementation details. elastic/kibana#153288