React: Upgrade to the new JSX transform

[youknowriad]

The next version of the WordPress packages is going to rely on the JSX transform after this Gutenberg PR ​https://github.com/WordPress/gutenberg/pull/61692

So this tickets tracks the backport of the webpack config change in that PR in order to be able to load the JSX runtime from the global variable.

Trac ticket: https://core.trac.wordpress.org/ticket/61324

Backports Gutenberg PR ​https://github.com/WordPress/gutenberg/pull/61692

This PR adds the necessary webpack config to build the React JSX Runtime script and adds the script to WordPress. Without this, the next package update on Core will be blocked as the new packages are going to be using the new JSX Runtime.

For the moment though, you can test that the PR adds the react-jsx-runtime script to wp-includes/js/dist/vendor/react-jsx-runtime.js
Also if you load manually the react-jsx-runtime in WordPress, you'll see the ReactJSXRuntime global available in the console.

[ellatrix]

In 58271:

React: Upgrade to the new JSX transform.

See ​https://github.com/WordPress/gutenberg/pull/61692.
See ​https://github.com/WordPress/wordpress-develop/pull/6678.

Props youknowriad.

Fixes #61324.

[ellatrix]

In 58273:

Add missing vendors file after r58271.

See #61324.

[desrosj]

In 58408:

Coding Standards: Apply changes after running composer format.

This applies several formatting related changes made while running composer format.

Follow up to [55720], [58171], [58271], [58282], [58283], [58292], [58299], [58303], [58332].
See #51857, #60719, #60895, #61021, #61118, #61228, #61276, #61324.

In 6.6 we tried moving away from the deprecated React UMD builds, the issue we faced is that there's a warning that is triggered on the console because we're not using a separate impact for createRoot. (SCRIPT_DEBUG true and npm run build)

Warning: You are importing createRoot from "react-dom" which is not supported. You should instead import it from "react-dom/client".

This warning has been removed in React 19 though along with the removal of the UMD builds, so we should be able to revert this PR when we upgrade to React 19.

@youknowriad, can you share testing instructions for the core? From our Slack conversation, I remember that some changes were required for wp-env.

Yes, so to reproduce the issue on core, you have to use the "build" folder in your environment so

• in .env file, you can change the LOCAL_DIR to build instead of src
• run npm run build
• run npm run env:start to launch the environment

you should be able to see the issue in trunk but not in this PR.

[youknowriad]

In 58775:

Build Tools: Use umd builds provided by React instead of bundling our own builds.

We tried moving away from the deprecated React UMD builds previously,
the problem we faced is that there's a warning that is triggered on the console because we're not using a separate impact for createRoot.

This warning has been removed in React 19 along with the removal of the UMD builds, so we should be able to revert this commit when we upgrade to React 19 but for now, we need to restore the usage of the umd builds.

Props mamaduka.
See #61324.

Commit https://core.trac.wordpress.org/changeset/58775