Reject events promises when the client is disconnected

[nathan818fr]

First commit

Fixes an issues where concurrent close calls don't call all the callbacks.

const chrome = await Chrome();
chrome.close(() => console.log('1'));
chrome.close(() => console.log('2'));

Before: Only 2 was printed.
After: Both 1 and 2 are printed.

Side-note: not calling the 'disconnect' event on user-initiated close seems like a strange API design decision.
I kept this behavior here, but I think you should consider changing this in the future (or at least add an event emitted in both cases).

Second commit

Ensures that promises waiting for CDP events are rejected when the client disconnects.
It's like #489, but for the events instead of commands.

const chrome = await Chrome();
const promise = chrome.Page.loadEventFired();
chrome.close();
await promise;

Before: The promise was waiting forever.
After: The promise is rejected with a 'client disconnected' error.