Added a test runner module
Added unit test for running arguments through the RunnerClient
Reformat the low data that is passed to RunnerClient's master_call

Closes #15218
Revert "send entire load to RunnerClient.async"

This is a precautionary revert to avoid unintended side effects.

This reverts commit 2ae993ac2474143a75f6e50c3659e870f57cb122.
Merge pull request #16331 from whiteinge/wrap-runner-master_call

Fix the call to RunnerClient().master_call()