IF: P2P: Send handshake to peer to let it know it is not syncing from peer

[heifner]

Test failure: nodeos_forked_chain_if_lr_test https://github.com/AntelopeIO/spring/actions/runs/8624067947/job/23638727644
The logs showed the test failed because a peer (Node02) stopped receiving blocks. It stopped receiving blocks because the block producer (Node00) thought Node02 was syncing from it, so it didn't send current blocks.

Updated net_plugin to send handshakes (how a node knows a peer is not syncing from it) even if the peer thinks the other peer is syncing from the you. Also send handshake to peer when it informs you that it needs blocks, but you determine it does not.

Set peer_syncing_from_us to false for handshake case where it was missing (Block discrepancy is within network latency range).

[ericpassmore]

Note:start
group: IF
category: INTERNALS
summary: More robust handshaking, send handshake to current peers, this allows nodes to discover they are not syncing from peers.
Note:end