[Feature Request][Go SDK]: Rewrite the `dot` runner in terms of a Portable pipeline.

### What would you like to happen?

The Go SDK's `dot` runner current generates a pipeline graph based on the Go SDK internal structures.

https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/core/util/dot/dot.go#L89

If it were rewritten in terms of the portable pipeline proto (https://github.com/apache/beam/blob/master/model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto#L91) then it could be used to render Cross Language pipelines and be used as a basis for the stand alone Prism Runner's web UI.

That would sufficiently allow #25896 to be closed.

### Issue Priority

Priority: 3 (nice-to-have improvement)

### Issue Components

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