idl-compiler: add serialization callback interface
idl-compiler: add serialization callback interface

Signed-off-by: Paweł Dziepak <e29bb3265626c60caf76d587cabdfcd8b379ef80@scylladb.com>

avikivity/scylla,scylladb/scylla,scylladb/scylla,raphaelsc/scylla,raphaelsc/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,kjniemi/scylla,kjniemi/scylla,duarten/scylla,kjniemi/scylla,duarten/scylla,avikivity/scylla,raphaelsc/scylla