rpc: use peer_id, blockhash for FetchBlock

Summary:
This concludes backport of core#23706 and core#24806
https://github.com/bitcoin/bitcoin/pull/23706/commits/923312fbf6a89efde1739da0b7209694d4f892ba

Depends on D12720

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12721