Rewrite runloop guide autorun FAQs

A rewrite of the autorun FAQs in the Runloop guide.

Fixes #1712 #1713 Partially addresses #1390
That is also not relevant. Even if Ember handled the click first, there would not be a runloop present.

The runloop is synchronous and blocking. It wraps function calls and returns just like any other function. It cannot leak between event handlers (excepting auto-runs, which explicitly break this behavior).

I know I'm being pedantic, but to write the guide you must learn the topic really well :-) I hope this is helping!