Jenkins Pipeline Updates (#2815)

Pipeline updates:
- get `gh` location on remote machine and define global bash env
variable `$GH` for GitHub CLI
- Failed cases are now displayed accordingly in the Jenkins dashboard
(see NOTE below)
-  Added the Build # in messaging for clarity when running from re-runs.
- Replaced Matrix construct for concurrency with the parallel method
that can use dynamic case lists
- With removing of the hard coded list of cases we now get list of cases
dynamically from the PR case directory
- See new look of dashboard below (has more annotations and displays
only used cases)

NOTE: **failFast** (quitting all cases on failing of one) still does not
work because it isn't quitting the running remote shells. We can make
this a configurable capability in feature request with some custom code.
The current behavior has the remaining cases continuing to run after a
FAIL label has been issued and it is incumbent of the code manager to
kill the CI job in the controller before resetting another Ready label.

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Co-authored-by: David Huber <[email protected]>