message: RegularQuicPacketBuilder::Packet -> PacketBuilderInterface::Packet
  Summary: as title
diff: @@ -42,6 +42,20 @@ class PacketBuilderInterface {
  public:
  virtual ~PacketBuilderInterface() = default;
  + // TODO: Temporarly let this interface be reusable across different concrete
  + // builder types. But this isn't optimized for builder that writes both header
  + // and body into a continuous memory.
  + struct Packet {
  + RegularQuicWritePacket packet;
  + Buf header;
  + Buf body;
  +
  + Packet(RegularQuicWritePacket packetIn, Buf headerIn, Buf bodyIn)
  + : packet(std::move(packetIn)),
  + header(std::move(headerIn)),
  + body(std::move(bodyIn)) {}
  + };
  +
  virtual uint32_t remainingSpaceInPkt() const = 0;
  // Functions to write bytes to the packet
  @@ -68,16 +82,7 @@ class RegularQuicPacketBuilder final : public PacketBuilderInterface {
  RegularQuicPacketBuilder(RegularQuicPacketBuilder&&) = default;
  - struct Packet {
  - RegularQuicWritePacket packet;
  - Buf header;
  - Buf body;
  -
  - Packet(RegularQuicWritePacket packetIn, Buf headerIn, Buf bodyIn)
  - : packet(std::move(packetIn)),
  - header(std::move(headerIn)),
  - body(std::move(bodyIn)) {}
  - };
  + using Packet = PacketBuilderInterface::Packet;
  RegularQuicPacketBuilder(
  uint32_t remainingBytes,
  