messaging_service: allow any self-serializing type
messaging_service: allow any self-serializing type

Currently, messaging_service only supports sending types for which a read/
write function has been explicitly implemented in messageing_service.hh/cc.

Some types already have serialization/deserialization methods inside them,
and those could have been used for the serialization without having to write
new functions for each of these types. Many of these types were already
supported explicitly in messaging_service.{cc,hh}, but some were forgot -
for example, dht::token.

So this patch adds a default implemention of messaging_service write()/read()
which will work for any type which has these serialization methods.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

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