Sorting pending builder each time the list is updated is unnecessary overhead. This can be done once the list is passed on to BuildRequestDistributor._activityLoop.

• I have updated the unit tests
• I have created a file in the newsfragments directory (and read the README.txt in that directory)
• I have updated the appropriate documentation

I was debugging some issues with BuildRequestDistributor and I find this change is an improvement of the existing implementation.
The question is, am I missing something? Is there actually any reason for the current implementation where pending builders are sorted each time the list is updated?

I will create newsfragment if the change is viable.