Extract smoke tests from automated commits

Summary:
Working on a land bot script that will call this, and there's no reason other
scripts shouldn't be able to call it as well.

Test Plan:
Sanity check that we didn't break anything:

COMMIT_TYPE=update-manpages ./automated-commits.sh -p <commit-hash-of-this-patch>

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5723