dillon1000/react

Deprecate ReactDOM.render and ReactDOM.hydrate (#21652)

* Use existing test warning filter for server tests

We have a warning filter for our internal tests to ignore warnings
that are too noisy or that we haven't removed from our test suite yet:
shouldIgnoreConsoleError.

Many of our server rendering tests don't use this filter, though,
because it has its own special of asserting warnings.

So I added the warning filter to the server tests, too.

* Deprecate ReactDOM.render and ReactDOM.hydrate

These are no longer supported in React 18. They are replaced by the
`createRoot` API.

The warning includes a link to documentation of the new API. Currently
it redirects to the corresponding working group post. Here's the PR to
set up the redirect: https://github.com/reactjs/reactjs.org/pull/3730

Many of our tests still use ReactDOM.render. We will need to gradually
migrate them over to createRoot.

In the meantime, I added the warnings to our internal warning filter.