stream: improve shutdown handling, minor clean up

- try to close as many things as possible when shutting down

- remove redundant (e.g. `exit` on process when
  listening for `close`) and straight up useless
  (`disconnect`) event listeners

package.json

@@ -25,6 +25,7 @@
     },
     "homepage": "https://github.com/wukko/cobalt#readme",
     "dependencies": {
+        "abort-controller": "3.0.0",
         "content-disposition-header": "0.6.0",
         "cors": "^2.8.5",
         "dotenv": "^16.0.1",