feat(cloudflare): cloudflare:fetch and cloudflare:durable:fetch hooks

[pi0]

This PR enables two new hooks:

• cloudflare:fetch(event)
• cloudflare:durable:fetch(event)

These hooks (while adding to complexity and runtime overhead) allow custom extensions to normal nitro lifecycle.

The main use case of this is for durable objects to allow redirect some requests from main worker to the single instance durable worker.

export default defineNitroPlugin((nitroApp: NitroApp) => {
  nitroApp.hooks.hook("cloudflare:fetch", async (event) => {
    // Force redirects all fetch requests to the durable object
    return event.durableFech();
  });

  nitroApp.hooks.hook("cloudflare:durable:fetch", async (event) => {
    console.log("Handling response in durable object:", event.url);
  });
});

With the above plugin, event in event handlers has event.context.cloudflare.context with the value of DurableObjectState type

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(this is mainly a draft idea; An alternative is to simply expose a method of direct fetch to durable)

[pi0]

Closing in favor of #3048, too much complexity and makes more edge cases if used wrongly, especially since we completely loose control over lifecycle