Gossip/Network module separation

Dependent on the review of #20056, as described here: https://www.notion.so/swirldslabs/Rpc-sync-Turtle-integration-23f7c9ab2591805d8677e646558a2b8a?source=copy_link under "Full separation of concerns"

Start by reviewing issue #20056 and the linked Notion page, especially the “Full separation of concerns” section. Identify the stated boundaries between the Gossip and Network modules and confirm the prerequisites from the RPC sync Turtle integration review. Done means the separation described there is implemented and validated against the project’s relevant checks.

Written by the indexing model from the issue text.