validation: move header validation error logging to VALIDATION debug category

Summary:
This is a backport of core#23235 [2/4]
https://github.com/bitcoin/bitcoin/pull/23235/commits/da94ebc2facd75c6105a7bd31765c6d2b37fc73b

Depends on D12038

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12039