Fix getServerSideProps hanging in dev on early end (#33366)

This fixes the case where calling `res.end()` is `getServerSideProps` would cause the request to hang in development due to our `Proxy` around `res` causing internal `ServerResponse` fields to not be available ([related post](https://javascript.info/proxy#built-in-objects-internal-slots)). I also migrated our `getServerSideProps` test suite to an e2e suite with a test for this case. 

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`

Fixes: #15118
Fixes: #32824
Closes: #33129

packages/next/server/render.tsx

@@ -961,7 +961,15 @@ export async function renderToHTML(
               warn(message)
             }
           }
-          return Reflect.get(obj, prop, receiver)
+          const value = Reflect.get(obj, prop, receiver)
+
+          // since ServerResponse uses internal fields which
+          // proxy can't map correctly we need to ensure functions
+          // are bound correctly while being proxied
+          if (typeof value === 'function') {
+            return value.bind(obj)
+          }
+          return value
         },
       })
     }

test/integration/getserversideprops/pages/another/index.js → test/e2e/getserversideprops/app/pages/another/index.js

@@ -1,17 +1,10 @@
 import Link from 'next/link'
+import path from 'path'
 import fs from 'fs'
-import findUp from 'find-up'
 
 export async function getServerSideProps() {
   const text = fs
-    .readFileSync(
-      findUp.sync('world.txt', {
-        // prevent webpack from intercepting
-        // eslint-disable-next-line no-eval
-        cwd: eval(`__dirname`),
-      }),
-      'utf8'
-    )
+    .readFileSync(path.join(process.cwd(), 'world.txt'), 'utf8')
     .trim()
 
   return {

test/e2e/getserversideprops/app/pages/early-request-end.js

@@ -0,0 +1,12 @@
+export function getServerSideProps({ res }) {
+  res.statusCode = 200
+  res.end('hello from gssp')
+
+  return {
+    props: {},
+  }
+}
+
+export default function Page(props) {
+  return <p>early request end</p>
+}