Fix loading react, react-dom, and react-dom/client.js for unit tests

[softwarenerd]

Description

This PR fixes how react, react-dom, and react-dom/client.js are loaded in unit tests. This fixes the unit test hang that was seen as a result of #5181.

QA Notes

yarn test-browser-no-install --browser chromium is now working again. If you run:

yarn test-browser-no-install --browser chromium --debug

You will see new output that shows how we are loading react-dom/client.js:

loader.js:1641 ------------------------------------------------------------------------
loader.js:1641 Changing where the react-dom client.js file is loaded from.
loader.js:1642 Original path: http://localhost:59048/46eec0d9769be1346e735ed63b8fd4da/node_modules/react-dom/umd/react-dom.production.min.js/client.js
loader.js:1643 Adjusted path: http://localhost:59048/46eec0d9769be1346e735ed63b8fd4da/out/react-dom/client.js
loader.js:1648 ------------------------------------------------------------------------

This work also fixes the long-standing warnings that were happening when loading the notebookServiceImpl.test module:

[petetronic]

Tested this branch locally, and with recompiling, confirmed that the browser chromium unit tests no longer hang 🎉