test: run test faster

[robertkowalski]

instead of using a timeout events are emitted which resulted in a 0.7s
runtime instead of a 1.3s lasting one

[robertkowalski]

Note: @isaacs mentions in #4932 that the usage of events instead of a timeout could make tests like this faster, however the fs.watch-Emitter does not emit a ready event like the new streams2 with readable so I used a custom event.

[bnoordhuis]

I landed a fix in c5ed96a that lowers the timeout from 1000 to 10 ms. Should work okay because the call to setTimeout() is only there in order to start the watcher on a later tick. I guess I could've used setImmediate() instead but meh, whatever - 1 or 10 ms doesn't affect the total run time, that's still around 250 ms. Anyway, thanks for pointing out the issue. :-)