update gossip

[turuslan]

• update gossipsub #297
• compare with rust-libp2p (old floodsub) (gossipsub)
• test gossip peer against mock streams/peers
• respect peer protocol version
• (rust) separate MessageCache (id and message data, gossip ihave, reply to iwant) and DuplicateCache (id only)
• (rust) gossip in heartbeat instead of publish/forward, may gossip same message to more peers in more heartbeats
• fanout peers (publish when we are not subscribed, like mesh but without explicit graft)
• send prune with backoff
• flood publishing (not same as floodsub)
• idontwant
• score
• opportunistic graft
• maintain outbound peer count in mesh
• fix Connectivity/Stream/GossipCore shared_ptr cycle/leak.
• remove hasTopic, add isSubscribed
• remove empty, add isUsed
• simplify stream write batch
• fix MessageReadWriterUvarint returned null for zero size message
• stubs: ExplicitPeers

[Copilot]

Copilot reviewed 35 out of 38 changed files in this pull request and generated no comments.

Files not reviewed (3)

• cmake/Hunter/config.cmake: Language not supported
• cmake/Hunter/init.cmake: Language not supported
• src/connection/CMakeLists.txt: Language not supported

Comments suppressed due to low confidence (1)

src/basic/message_read_writer_uvarint.cpp:47

• In the case where msg_len equals 0, 'buffer' is used without being declared. Consider returning an empty shared pointer (or an appropriate default value) instead of 'buffer' to prevent compilation/runtime issues.

cb(buffer);