Add Confluent-Client-Version header to requests to SR, Python client

[fangnx]

What

Checklist

• [ ] Contains customer facing changes? Including API/behavior changes
• [ ] Did you add sufficient unit test and/or integration test coverage for this PR?
  • If not, please explain why it is not required

References

JIRA: https://confluentinc.atlassian.net/browse/DGS-22770

Test & Review

Open questions / Follow-ups

[confluent-cla-assistant[bot]]

:tada: All Contributor License Agreements have been signed. Ready to merge.
_{Please push an empty commit if you would like to re-run the checks to verify CLA status for all contributors.}

[sonarqube-confluent[bot]]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube