This abstracts queue management, making it possible to implement different
policies for each team. It provides two concrete policies:
RotateAlphabeticallyReviewerQueuePolicy, which rotates an alphabetically
ordered reviewer list with consideration for skip indications, and is the
default policy; and LeastRecentlyUsedReviewerQueuePolicy, a simple
least-recently-used policy. Also see issues #2721 and #2656.
- Legacy-Id: 17121
