Add API URL to JIRA settings

What does this MR do?

It adds JIRA API url to the Jira Service settings. In case this url is not set the web url is taken as the api url.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

After we simplified the Jira Service settings users lost the possibility to set API url in case it differs from the Web url

Screenshots (if relevant)

Configuration

Links to Web url

You can check the comment was created correctly http://jira.gitlap.com:8080/browse/TEST-1

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #31448 (closed)