Improve Traceability of Pipeline translation

Users often ask how they can reason about the pipeline translation. The Flink UI display a confusingly large graph without any trace of the original Beam pipeline:

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Some aspects which make understanding these graphs hard:

• Users don't know how the Runner maps Beam to Flink concepts
• The UI is awfully slow / hangs when the pipeline is reasonable complex
• The operator names seem to use transform.getUniqueName() which doesn't generate readable name
• So called Chaining combines operators into a single operator which makes understanding which Beam concept belongs to which Flink concept even harder