log: improve some validation log messages to include hashPrevBlock

Summary:
Backport of core#26487

When there is an issue with a previous block the current log messages do
not indicate hashPrevBlock. Adding it makes debugging easier.

Test Plan:

ninja check check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12538