As indicated in #11816, we'd like to enable deserializing vectors in reverse.
The forward deserialization is achieved by reading from an input_stream. The
input stream internally is a singly linked list with complicated logic. In order to
allow for going through it in reverse, instead when creating the reverse vector
initializer, we scan the stream and store substreams to all the places that are a
starting point for a next element. The iterator itself just deserializes elements
from the remembered substreams, this time in reverse.
Fixes#11816Closes#11956
* github.com:scylladb/scylladb:
test/boost/serialization_test.cc: add test for reverse vector deserializer
serializer_impl.hh: add reverse vector serializer
serializer_impl: remove unneeded generic parameter
bd1fcbc38f