PR #19108 caused some Suspense-related DevTools regressions (more info available on #19368) which we did not catch because of the fact that DevTools tests are only run against the version of React in master.

We should follow the precedent of the regression fixtures tests and have CI run DevTools tests against multiple React versions, including v15, all v16 minors, and the current HEAD of master branch.

Setting this up will involve several things:

• Infra to checkout older React packages and run tests against them.
• Some form of gating so that we can account for expected differences in Store snapshots between React versions.
• Some form of gating so that we can avoid running tests against invalid combinations of features and versions (e.g. don't test for Suspense in a version of React that didn't include that component yet).