Handle `ErrorArtifact`s returned from tasks gracefully in a Pipeline/Workflow

[vachillo]

• [x] I have read and agree to the contributing guidelines.

Is your feature request related to a problem? Please describe. Currently, if a task in the middle of a Pipeline or Workflow returns an ErrorArtifact, the entire Structure short-circuits and ends. This can lead to a situation where the output_task output is None.

Describe the solution you'd like I would expect more graceful handling of ErrorArtifacts returned from tasks.

• a way to mark a Structure or individual Tasks as fail_fast = True/False to control this behavior.
• a way to "catch" ErrorArtifacts in a Pipeline or Workflow by specifying a Task that will be run only if an ErrorArtifact gets returned

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Lines in workflow.py that cause this behavior Lines in pipeline.py that cause this behavior