[JENKINS-74151] Extract inline onBlur and JS script in `ReleaseStep/config.jelly`

[shlomomdahan]

JENKINS-74151

WHY https://www.jenkins.io/doc/developer/security/csp/

Testing done

Before Changes:

https://github.com/user-attachments/assets/208319d0-022c-4c4b-9f1c-47a10863f277

After Changes:

https://github.com/user-attachments/assets/d82c4410-0fe0-40d4-9a66-d0140a842b82

Submitter checklist

• [x] Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• [x] Ensure that the pull request title represents the desired changelog entry
• [x] Please describe what you did
• [x] Link to relevant issues in GitHub or Jira
• [x] Link to relevant pull requests, esp. upstream and downstream changes
• [x] Ensure you have provided tests - that demonstrates feature works or fixes the issue