validation: put coins cache write log into bench debug log
validation: put coins cache write log into bench debug log

Summary:
This is a backport of [[https://github.com/bitcoin/bitcoin/pull/23235 | core#23235]] [4/4]
https://github.com/bitcoin/bitcoin/pull/23235/commits/b5950dd59ca3e144721a5f15568a65be43bd2f20

Depends on D12042

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12043

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