Rule Chain: Add the ability to run an individual rule directly from within the rule chain screen

Similar to how you can run a rule directly from the Rules List, it would be a timesaver (especially when testing) to be able to run a rule from directly within the Rule Chain screen as well.  Often when I'm testing, I'm testing in rule chain order. This would save me having to either search for the rule I want to run via Rules List or from the Rule Chain, click the rule, open for editing and navigating to the action screen and performing a test run.