rpc, test: expose CNodeStats network in RPC getpeerinfo

Summary:
This is a backport of core#20002 [2/5]
https://github.com/bitcoin/bitcoin/pull/20002/commits/4938a109adf13f2c60a50f08d4cc9ddb8d7ded96

Depends on D10502

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10503