OLAP Connectors: Test the connection before exiting the "Add Data" modal

[ericpgreen2]

This PR ensures that a connection to the OLAP database is successfully established before finalizing the creation of a connector.yaml file and updating the .env file. Previously, submitting the ClickHouse, Druid, or Pinot connector forms would create these files regardless of the validity of the credentials.

Implementation details:

• Optimistically create a connector.yaml file.
• Optimistically create or update the .env file with the provided credentials.
• Call the OLAPListTables API to verify the connection.
• If the connection fails, remove the connector file, revert the changes made to the .env file, and display an error message.

Once #6671 lands, we can potentially switch the implementation to use a tmp directory and, in particular, a tmp/.env file to test credentials.

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
• Intend to cherry-pick into the release branch
• I'm proud of this work!

[AdityaHegde]

Would be good to move this to a static method on ClickHouseTestContainer that also returns the instance.

[ericpgreen2]

I can't quite tell exactly what you have in mind? Regarding another layer of abstraction– that might be valuable, but I'd prefer not to add extra abstractions here before we know how our usage of this class will evolve. For example, I could especially see the seed method being parameterized based on which dataset you want to use for a given test suite.