Support ganged or multivalue Cmdline Option with subOptions

[hopscc]

Some commandline options provide multiple tweaks around a single item (e.g testify-threads, testify-runner, testify-results affecting -testify).

It would be convenient if rather than having multiple individual options for things like this we could specify a single option and provide a set of subOptions within it explicitly tying the subOptions to a single item
(also supporting defaulting and convenient ganged settings)

Useful also for setting things like metrics (enabling) and list of metrics (to be calculated) and arg provided to each metric to be done (threshold value).
see  Code Metrics Discussion

[hopscc]

Heres a patch for cmdline subOpts and mods of testify-* options to use -testifyArgs
with possible subOptions resultsFile, numThreads, runner.
Rel Note but no new tests. existing suites work as before for both single and multithread cases (testifyArgs:numThreads=2).

[hopscc]

In the patch in Commandline.cobra ignore/elide/remove the new 'metrics' cmdline arg optionSpec clause... Its for a follow-on still partially baked enhancement...