[Part 1] Refactor logging code into a global object

Summary:
MOVEONLY: Move logging code from util.{h,cpp} to new files.

Break logging code out of util.{h,cpp} into logging.{h,cpp}. This does not modify anything, just moves code.

Test Plan:
Run bitcoind with different permutations of:
-logtimestamps, -debug, -printtoconsole, -datadir, -shrinkdebugfile

Reviewers: deadalnix, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: deadalnix, O1 Bitcoin ABC, #bitcoin_abc

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1280