Add mock for sql datasources that have connectivity issues

[scottlepp]

This allows us to mock sql datasources that we have problems connecting to: SAP Hana, Databricks, Oracle, etc. Some of these sql datasources require a paid account or only provide temporary evaluation period. This can block development and make e2e testing impossible.

This mocking allows doing some simple local development, compatibility testing and e2e testing against sql plugins that are otherwise unable to get a real connection, or setting up a connection with docker etc is difficult.

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