CMS 5: UploadFieldEntwine.js uses deprecated ReactDOM.render()

[GuySartorelli]

silverstripe/silverstripe-admin#1312 involved updating a lot of code, but some work was left undone.

src/entwine/UploadField/UploadFieldEntwine.js defines how entwine hooks result in the react UploadField being added to the DOM.
It includes a deprecated use of ReactDOM.render() in its refresh() function.

This was necessary because replacing it with the new React 18 createRoot() syntax resulted in an infinite loop any time a form in the CMS was submitted which included changes to the value of an UploadField (e.g. add a file and then save page, or remove file and then save page).
Worth noting here that the form submission did work correctly - refreshing the page shows the new value. So it's purely a react rendering issue after the submission has occurred - possibly some race condition between react and entwine.

Replace the ReactDOM.render() syntax with createRoot(), and refactor whatever needs refactoring to avoid the infinite loop on form submissions.

Acceptance Criteria

• We don't use the deprecated ReactDOM.render()
• The upload field works correctly in entwine forms
• Forms submit correctly when saving changes to upload fields