Initial version of the swh.objstorage.replayer package
this consists in the copy and adaptation of content replayer related files from swh.journal v0.0.31.
Notable modifications:
- test_write_replay.py has been merged into test_replay.py,
- any reference to swh.journal.replay has been replaced,
- adapted cli module to make added replayer commands subcommands of the objstorage's main cli group,
- drop usage of vcversionner in favor of setuptools_scm.
Migrated from D3071 (view on Phabricator)