Update terminology on JenkinsRule and deprecate methods

[jonesbusy]

Update terminology on JenkinsRule.

Keep existing *slave methods and deprecate them

Testing done

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1. Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
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5. Link to relevant pull requests, esp. upstream and downstream changes
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[MarkEWaite]

Thanks

[jglick]

#337 (comment) IMO