util, refactor: Drop explicit conversion to fs::path

Summary:
Removes unhelpful noise/verbosity.
See: https://github.com/bitcoin/bitcoin/pull/24306#discussion_r809363741

This concludes backport of core#24675
https://github.com/bitcoin/bitcoin/pull/24675/commits/b01f336708019f8c8274ea701d3446e4123e7af2

Depends on D16200

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16201