Move -checkblocks LogPrintf to AppInitMain

Summary:
Partial backport of core#23280:
https://github.com/bitcoin/bitcoin/pull/23280/commits/8d466a8504bfb81ce8699d650aa72ec9cc8b0a54

Depends on D12572.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D12573