Sometimes the user list was incomplete when multiple requests were
created to fetch next pages. If the responses did not arrive in the
same order as the requests then only the last response was parsed.
This is a follow up commit to a0f4c7fe888af75424d5beaf4d17630e4d49f0fa.
We want to wrap the `Ember.run.debounce` function and internally call `Ember.run` instead when running tests.
This commit changes discourseDebounce to work the same way as `Ember.run.debounce`.
Now that `discourseDebounce` works exactly like `Ember.run.debounce`, let's replace it and only use `DiscourseDebounce` from now on.
Move debounce to discourse-common to be able to reuse it in different bundles
Keep old debounce file for backwards-compatibility
