We need a better way to handle node.js + pthreads errors

With the changes made in #9863 errors in a node.js pthread are reported like `pthread sent an error! undefined:undefined: Module is not a function`.
This could be more helpful, it would be good to get a line number and file like we do in the web case. At a minimum `undefined:undefined` should go.

My suggestion would be to replace
https://github.com/emscripten-core/emscripten/blob/408a6e9411165fdfd3c18163f37ee302e751857d/src/library_pthread.js#L441
with `err('pthread sent an error!\n' + data.stack);`. This will print out something like:
```
pthread sent an error!
TypeError: Module is not a function
at onmessage (/path/module.worker.js:93:16)
[stacktrace continues]
```
This is slightly more helpful. However I'm not familiar enough with node to know if there's something better.
Anyone have any better ideas?