This new component broadcasts metrics about the current size of the pinqueue,
which can in turn be used to inform allocations.
It has a weight_bucket_size option that serves to divide the actual size by a
given factor. This allows considering peers with similar queue sizes to have
the same weight.
Additionally, some changes have been made to the balanced allocator so that a
combination of tags, pinqueue sizes and free-spaces can be used. When
allocating by [<tag>, pinqueue, freespace], the allocator will prioritize
choosing peers with the smallest pin queue weight first, and of those with the
same weight, it will allocate based on freespace.
4daece2b98