Better integrate pipeline validation

[tpluscode]

I propose that we make validation an integral part of barnard CLI

• [ ] Fail fast: Executing barnard59 run should implicitly validate a pipeline at the beginning and stop when error are found
• [ ] Opt out: To disable validation, add a flag barnard59 run --no-validate
• [ ] Separate CLI command: barnard59 validate

Validation should use the existing barnard59-pipeline-validation

[tpluscode]

As proposed by @giacomociti we may actually remove the CLI part from barnard59-pipeline-validation and keep it only as a library

The CLI would be moved to barnard59