add getMaxTotalUses

[vineeth-bandi]

Added the method getMaxTotalUses which fixes Issue #397

Testing done

Verified that set value for Max Total Uses persists through config save and apply on Jenkins version 2.277.2 and 2.414. Previous behavior with lack of getter method was to replace with default value of -1 every time on Cloud Configuration page.

Submitter checklist

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