Investigate moving more complex workflows to the Pipeline plugin

[mmitche]

Investigate moving more of the complicated multi-machine workflows to "pipeline".

There will be some challenges:

• Still need to create the pipeline job, so job dsl will have to integrate.
• Pipeline text could be checked in and read from git during job creation, but you can't execute workflow jobs directly for each check-in/PR from the enlistment, since it allows you to alter what machines things run on. we could potentially work around this some other way
• There are inter-project dependencies CoreFx requires the CoreCLR build artifacts from the mid-stage of the CoreCLR test pipeline for non-Windows OS's. This probably isn't hard to deal with (add a separate pipeline for the CoreCLR build)
• We use a lot of extra features on the job - timeouts, workspace wiping, etc. that needs to stick around.

/cc @sejongoh