[BYON] Emit multiple recommendations per validation

[tumido]

Instead of finding a single violation and exiting the validation, continue if possible and raise as many recommendations possible. Gather Recommendations in NDJSON format, so it can be easily serialized later in an imagestream update step. Message format:

{"severity": "error", "message": "Python not found"}
{"severity": "warning", "message": "Package 'non-critical-package' not installed"}

Action item: decide if validation should fail on any error (including recommendations) or we should let the validation pass if only certain severity is present.
Note: we may need to use workspaces to pass extra data, since Tekton has results limit size at 4096 bytes https://tekton.dev/docs/pipelines/tasks/#emitting-results