Move version comparison utility functions to their own file

Summary:
In order to migrate archive-release-notes and the AUR automation
according to D7442, we need a better way for these utility functions to
continue to be shared.

Test Plan:
With this patch applied, create a version bump commit to trigger release notes archiving:

sed -i 's/VERSION 0.22.2/VERSION 0.22.3/g' CMakeLists.txt
git add -u
git commit -m "version bump"

Test:

COMMIT_TYPE=archive-release-notes ./automated-commits.sh -p HEAD
git show     # verify release notes are archived as expected

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7449