dillon1000/react

Adding some server rendering unit tests. (#9055)

* Added a handful of SSR unit tests, ported from a previous pull request.

* Fixing linting errors

* Fixed a test helper function to properly report errors.

* Un-nested the new rendering tests. Updated the fiber test passing/not passing lists.

* Edited to comply with the react/jsx-space-before-closing eslint rule, which will soon be merged into master.

* Response to code review from @spicyj. Moved tests to separate file, reworked wording of test names, corrected use of canUseDom, and simplified tests against tagName. Thanks for the help, @spicyj!