chore(templates): update cloudflare templates to support streaming and `defer` in entry.server.tsx

[dgurns]

The cloudflare-pages and cloudflare-workers templates had been updated to React 18, but do not currently support streaming responses and defer.

This PR:

• Updates those templates to do so. Now a new project initialized with either of those templates should support defer out of the box.
• Updates the docs for defer to include steps on how to upgrade an older Remix app to support defer, including necessary changes in entry.client.tsx and entry.server.ts that enable client-side React 18 hydration and streaming responses.

I pulled the entry.server.tsx code from @jacob-ebey's example project which deploys to Cloudflare and also tested it successfully on my own project.

Thanks for all your great work and very excited to begin playing around with defer.

[changeset-bot[bot]]

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Latest commit: 704fc042be715857e97621442605e49113a4a3cc

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[machour]

@dgurns was this closed by mistake?

[dgurns]

Woah weird. Yeah didn't mean to close it. I think I clicked "sync fork" on Github and something happened ha! I'll look into it and reopen.

[dgurns]

Opened a new PR #5298