Improvement: align CI with test harnesses

[chesedo]

Details
In #231 the CI is made to use the same script as the local testing harness for postgres integration. The idea is to keep to two from becoming out of synth and to make it easy to perform local e2e testing.

The same alignment should happen for:

• mysql (synth/testing_harness/mysql) (ci: align test harness #246)
• mongo (synth/testing_harness/mongo) (ci: align test harness #246)
• sqlite? feat: support sqlite #185