Move init logistics message for BAD_GENESIS_BLOCK to init.cpp

Summary:
Partial backport of core#23280:
https://github.com/bitcoin/bitcoin/pull/23280/commits/975235ca0a8f5bcf9df880698b3b0d4bbde9f7fb

Depends on D12567.

Test Plan: Read the comment.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D12568