docs: improve jobs autorun docs, adds e2e test (#12196)

This clarifies that jobs.autoRun only *runs* already-queued jobs. It does not queue the jobs for you.

Also adds an e2e test as this functionality had no e2e coverage

test/plugins/int.spec.ts

@@ -17,9 +17,7 @@ describe('Collections - Plugins', () => {
   })
 
   afterAll(async () => {
-    if (typeof payload.db.destroy === 'function') {
-      await payload.db.destroy()
-    }
+    await payload.destroy()
   })
 
   it('created pages collection', async () => {