-maxapsfee: follow-up fixes

Summary:
Co-authored-by: Jon Atack <jon@atack.com>
Co-authored-by: Samuel Dobson <dobsonsa68@gmail.com>

This is a backport of core#19743

Notes:

• the Release notes are not relevant because they refer to a PR that we backported almost one year ago.
• the formula for computing a defaulti fee in Bitcoin ABC is 1 sat/byte * tx_size, with tx_size ~ 148 * n_in + 33 * n_out + 10. The tx sizes in the log messages checked in this PR are consistent with this formula (and different from the way Core computes the fees).

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10094