Fix unhandled rejections with edge runtime (#39091)

This corrects some unhandledRejection errors showing when a connection is canceled with the edge runtime since the changes needed for 14463dd. This also adds a regression test to ensure we don't have these class of errors in our middleware tests. 

## Bug

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

Fixes: [slack thread](https://vercel.slack.com/archives/C03Q1UU3Z4H/p1658960102013969)

packages/next/server/body-streams.ts

@@ -56,9 +56,13 @@ export function getClonableBody<T extends IncomingMessage>(
 ): ClonableBody {
   let buffered: Readable | null = null
 
-  const endPromise = new Promise((resolve, reject) => {
-    readable.on('end', resolve)
-    readable.on('error', reject)
+  const endPromise = new Promise<void | { error?: unknown }>(
+    (resolve, reject) => {
+      readable.on('end', resolve)
+      readable.on('error', reject)
+    }
+  ).catch((error) => {
+    return { error }
   })
 
   return {
@@ -69,7 +73,11 @@ export function getClonableBody<T extends IncomingMessage>(
      */
     async finalize(): Promise<void> {
       if (buffered) {
-        await endPromise
+        const res = await endPromise
+
+        if (res && typeof res === 'object' && res.error) {
+          throw res.error
+        }
         replaceRequestBody(readable, buffered)
         buffered = readable
       }

test/e2e/middleware-rewrites/test/index.test.ts

@@ -680,6 +680,11 @@ describe('Middleware Rewrite', () => {
         logs.every((log) => log.source === 'log' || log.source === 'info')
       ).toEqual(true)
     })
+
+    it('should not have unexpected errors', async () => {
+      expect(next.cliOutput).not.toContain('unhandledRejection')
+      expect(next.cliOutput).not.toContain('ECONNRESET')
+    })
   }
 
   function getCookieFromResponse(res, cookieName) {