Instruct runTheMatrix to throw an exception if a non defined workflows is required

[fabiocos]

This issue is meant as a follow up of the comment #27678 (review) about instrumenting the runner to throw an exception in case a non defined workflow is requested

[cmsbuild]

A new Issue was created by @fabiocos Fabio Cossutti.

@davidlange6, @Dr15Jones, @smuzaffar, @fabiocos, @kpedro88 can you please review it and eventually sign/assign? Thanks.

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[fabiocos]

assign pdmv

[cmsbuild]

New categories assigned: pdmv

@pgunnell,@prebello,@zhenhu you have been requested to review this Pull request/Issue and eventually sign? Thanks

[fabiocos]

A solution (not in the Runner but directly in runTheMatrix) has been implemented in #27713
@slava77 FYI