using another source of gossip with the gossip sync

We should try to integrate the https://lightningdevkit.org/blog/announcing-rapid-gossip-sync/ feature of ldk inside core lightning and see if we have some improvement

See an example here https://github.com/ffaex/altpay

Start by reading the LDK Rapid Gossip Sync announcement and the linked altpay example, then inspect this Rust repository's Core Lightning pay-plugin integration. The issue does not name files or tests; completion would require integrating the gossip-sync approach and demonstrating an improvement.

Written by the indexing model from the issue text.