OLAP Connectors: Add DSN configuration option

[ericpgreen2]

Closes #6579

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated (FYI @royendo for docs updates, please!)
• Intend to cherry-pick into the release branch
• I'm proud of this work!

[royendo]

definitely will need to look at revisiting
https://docs.rilldata.com/reference/olap-engines/clickhouse but that seems to be about it :)

[ericpgreen2]

definitely will need to look at revisiting https://docs.rilldata.com/reference/olap-engines/clickhouse but that seems to be about it :)

Sounds good – just note that Druid & Pinot will have this DSN option too

[k-anshul]

LGTM from an experience POV.

One minor thing that I noticed(exists on main not introduced in this PR) is that if clickhouse modeling is disabled then I can't add one more clickhouse connection from UI. The data option is hidden. I need to manually create another connection.yaml

[ericpgreen2]

One minor thing that I noticed(exists on main not introduced in this PR) is that if clickhouse modeling is disabled then I can't add one more clickhouse connection from UI. The data option is hidden. I need to manually create another connection.yaml

Thanks, Anshul. Addressed this comment here: #6904