Implement a circular buffer double ended queue for quotas `RefundQueue` instead of a vec

In !183 (merged), I wanted to use a BoundedVecDequeue, but it is not implemented in substrate yet.

See discussion !183 (comment 38444) for details.

changed milestone to %Horizon

mentioned in merge request !183 (merged)

added I-ToPrioritize label

added C-runtime D-easy ET-days P7-nicetohave labels and removed I-ToPrioritize label

No need for double ended queue, we only push refund requests at the end and pop at the start (simple queue).

One question is: when the queue is full, do we throw away the oldest requests to store the new ones, or do we dismiss the new ones to honor the oldest ones?

added S-needdiscussion label

removed milestone %Horizon

removed C-runtime label

removed ET-days label