Replaces std::deque with quiche::QuicheCircularDeque in http2::PriorityWriteScheduler.
Replaces std::deque with quiche::QuicheCircularDeque in http2::PriorityWriteScheduler.

std::deque allocates a 4kB block, even if it's only storing a single element:
  http://google3/third_party/crosstool/v18/stable/installs/llvm/include/c++/v1/deque;l=294;rcl=438152875

QuicheCircularDeque should be a much more efficient data type for small container sizes.

PiperOrigin-RevId: 439672104

google/quiche,google/quiche,google/quiche,google/quiche