[yaml] propogate error_handling to windowing composite config

[Polber]

There was a bug with pipeline-level windowing with transforms that define error_handling in which pipelines would fail with error:

Ambiguous output at line 16: Stream has outputs [None, 'errors']

This was due to a check to ensure a transform only outputs a "good" collection and optionally a collection defined by the named output in the error_handling config. Since the error_handling was not propagated to the top-level composite constructed as part of pipeline-level windowing, the check would fail.

Example affected pipeline:

pipeline:
  transforms:
    - type: ReadFromPubSub
      name: Stream
      config:
        topic: projects/pubsub-public-data/topics/taxirides-realtime
        format: json
        schema:
          type: object
          properties:
            ride_id: {type: string}
        error_handling:
          output: errors
    - type: LogForTesting
      name: Log messages
      input: Stream
    - type: LogForTesting
      name: Log errors
      config:
        level: INFO
      input: Stream.errors
  windowing:
    type: fixed
    size: 60
options:
  streaming: true

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[Polber]

R: @robertwb

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[robertwb]

Thanks for finding and fixing this.