Support databricks policy id for setup_stitch and launch_job commands

[avivshafir]

This pull request introduces support for passing an optional cluster policy ID (policy_id) when launching Databricks jobs, and Stitch setup command.

For example:

/setup-stitch --auto-confirm --policy_id=000F957411D99C1F

Previously the passed command arguments were being ignored (auto confirm didn't work)

Related issue: #43

[pragyan-amp]

Hi @avivshafir Thanks a lot for raising the PR.

can you take some time to add tests for following:

• policy_id being passed through /launch_job
• policy_id being passed through /setup-stitch --auto-confirm
• policy_id in interactive mode
• for the service.py fix (argument parsing for interactive commands)

Will get it merged once these are validated..