Add CI for Python code

[snazy]

Describe the bug

Polaris Python API bindings and Polaris-Client need to be covered in CI.

To Reproduce

No response

Actual Behavior

No response

Expected Behavior

No response

Additional context

No response

System information

No response

[MonkeyCanCode]

@snazy thought we already have https://github.com/apache/polaris/blob/main/.github/workflows/regtest.yml for this?