test: stub connection in unit test to emulate multi adapter support within the same suite

[mberlanda]

Tests are currently running assuming the adapter is always sqlite.
This PR introduce:

• a check to use the stub a connection based on the adapter in use
• added tests for statement adapter
• stub correctly the connection to avoid to apply always sqlite quoting
• add missing test cases to ci

[mberlanda]

mysql suite is still not passing due to:

• boolean represented sa tinyint
• some tests assuming sqlite as default adapter
• trying to perform real inserts with pg adapters

Count of failing tests: 6

They are going to be addressed in a separated PR