Add option to disable printing workflow outputs

[bentsherman]

This PR adds the ability to disable printing workflow outputs by specifying -output-format none

It also improves the workflow output printing logic by (1) using an onComplete handler instead of an igniter and (2) not printing in the event of a pipeline error

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[rpetit3]

Playing around with the latest edge release, I wonder if an option to output to a json file might also be useful. (I may have also missed that!)

For a single sample, using -output-format json 2894 lines are the outputs in JSON format, and 113 lines are related to the the pipeline. text produces less, but I think users will still be confused (e.g. "was some debug text left in?).

I think my usage would be to default to none then when debugging switch to json or json file if available.

I do recognize this as super useful information to have on hand to review/testing/debugging.

[bentsherman]

For that the idea is to use -q with -output-format json to suppress all other output and just print the JSON. Then you can redirect stdout to a file. This is similar to how nextflow inspect works, except nextflow inspect sets -q automatically

[jorgee]

Changes look fine to me. Just a minor comment, shouldn't be better to set default to none for the CmdRun case to work as in the previous version?

[bentsherman]

Thanks Jorge. Since workflow outputs are still new and we want to promote it, I think it's fine to have it enabled by default. Also for consistency with nextflow module run which prints the human-readble outputs by default.