Use C++11 member initializer in CNodeState

Summary:
This is a backport of core#21370 and core#21424 (partial)
https://github.com/bitcoin/bitcoin/pull/21424/commits/6927933782acb9b158787e6f35debb916793f6b1

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13303