modp2p: increase the SeenMessage interval in PubSub

[Wondertan]

We periodically receive old headers from the network that were already synced. Increasing the seen message interval should decrease those.

The only downside is that it may eat slightly more RAM, but it will improve GossipSub peering behaviors. Instead of punishing outdated messages as invalid, it will only reduce communication with the peer. This is especially important when the new CHOKE msg is introduced in the GossipSub v1.2

[Wondertan]

I looked it up, and its 2min by default, which means either:

• we end up receiving headers with 2mins delay
• we have several valid headers per height with different hash