For a niche opt-in feature, checking if the tenants table is in the current schema is good enough for determining if the current DB is central -- the solution where we added getCurrentDatabaseName to each manager was overly complicated for this (though a bit more correct, not worth the added complexity).
Make hardening work correctly even for named SQLite DBs, also make the related test test named SQLite DBs instead of just MySQL (the SQLite dataset fails when the DatabaseTenancyBootstrapper changes get reverted).
"database tenancy bootstrapper throws an exception if DATABASE_URL is set" was failing with the null $databaseUrl because the tenant DB was never created. This test was ignored during test runs because the test file lacked the 'Test' suffix.
