move sql files in the package and update tests according to D538
make sql db init files part of the python package and use them to initialize the db used for tests. Also kill now useless sql/Makefile.
Related to swh-storage#1265 (closed).
Test Plan
with swh-core!16 (closed) applied in swh-core, all tests should pass like: swh-archiver$ pifpaf run postgresql nosetests
Migrated from D539 (view on Phabricator)