CSP compatibility improvements

[zbynek]

Somewhat related to https://issues.jenkins.io/browse/JENKINS-73166 which showed that geval is used by this plugin.

This PR reduces usages of inline JS to improve CSP compatibility.

Testing done

Manually checked that the affected functionality is still OK:

• certificate can be uploaded, validated and updated
• new domain creation: submit button deactivates for empty name, auto-focus works
• same for domain configuration
• help for "include user credentials" working (in a job parameter)

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
• [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue