feat(renderer): add `render:before` hook

[pi0]

(context: Discussion with @atinux regarding how to set cache callback options to the renderer handler. This PR, adds a primitive to allow it with advanced usage)

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This PR adds a new render:before runtime hook support for renderer handlers (like Nuxt SSR). This hook allows to customize rendering behavior by intercepting the context:

• Render function can be overridden or wrapped by setting context.render
• A response can be directly generated/handled by setting context.response

Usage is not restricted to caching only and it allows more general customization of renderer behavior but for particularly caching purposes here is an example:

import { defineNitroPlugin, defineCachedFunction } from "nitro/runtime";

export default defineNitroPlugin((nitro) => {
  const cache = new WeakMap();
  nitro.hooks.hook("render:before", (ctx) => {
    let render = cache.get(ctx.render);
    if (!render) {
      render = defineCachedFunction(ctx.render, {
        // Custom cache options
        maxAge: 60_000,
        shouldBypassCache: (event) => { /* custom logic */ }
      });
      cache.set(ctx.render, render);
    }
    ctx.render = render;
  });
});