Test Details Overview

Deduplicate network messages through `transport::message_filter` (#5277)

`nano::transport::message_filter` is now what the network holds as its
duplicate filter. It says which messages are deduplicated, publishes
and votes, hashes a payload together with what its header says the
payload is, and does the locking. `nano::duplicate_filter` under it is
a plain table of digests: it takes bytes and a domain the caller
picks, knows nothing of blocks or messages and holds no lock.

A digest covers the message type and, for a publish, the block type
along with the payload, so two kinds of message with equal payloads
are two entries. Header flags and versions stay out of it, which keeps
a rebroadcast vote a duplicate of the vote.

The check moves from `deserialize_message_payload` to `tcp_server`,
which reads the header and the payload and was the only caller that
filtered. The deserializer takes the digest to put on the message
instead of the filter, and `deserialize_message` no longer takes one.

`duplicate_filter_enable` in the network config turns deduplication
off.

`message_filter` has its own test suite, one case of which has several
threads insert the same digest at once, and the `tcp_server` tests
cover messages with equal payloads, messages that are not
deduplicated, a publish the block processor refuses and the config
switch. The filter benchmark measures both classes: the plain filter
on one thread, as it holds no lock, and `message_filter` on 1 to 16
threads, with the inserts all threads make per second. Its clock
scenarios go.

__________

Type: commit

Hash: fe4397213eb8fcf80f59c6e2f0a614b03cf449ee

Created: today

__________

gr0v1ty/nano-node:fe4397213eb8fcf80f59c6e2f0a614b03cf449ee