Prepare backports in the logger

Summary: This change the name of variosu variables to make them consistent with Core's logger, which will make backports easier.

Test Plan:

make check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox, teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1944