CWallet::Create move chain init message up into calling code
Summary:
This is a partial backport of core#20773
https://github.com/bitcoin/bitcoin/pull/20773/commits/d73ae939649f3b30e52b5a2cccd7fafd1ab36766
Depends on D17643
Test Plan: ninja all check-all
Reviewers: #bitcoin_abc, roqqit
Reviewed By: #bitcoin_abc, roqqit
Differential Revision: https://reviews.bitcoinabc.org/D17644