quic: avoid memory fragmentation issue

Original PR: https://github.com/nodejs/quic/pull/388



Previously, QuicPacket was allocating an std::vector<uint8_t> of
NGTCP2_MAX_PKT_SIZE bytes, then the packet would be serialized into the
buffer, and the std::vector would be resized based on the number of
bytes serialized. I suspect the memory fragmentation that you're seeing
is because of those resize operations not freeing memory in chunks that
are aligned with the allocation. This changes QuicPacket to use a stack
allocation that is always NGTCP2_MAX_PKT_SIZE bytes and the size of the
serialized packet is just recorded without any resizing. When the memory
is freed now, it should be freed in large enough chunks to cover
subsequent allocations.

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/33912


Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>