[BEAM-2884] Move DoFnInfo to SDK util

[kennknowles]

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Previously, the DoFnInfo wrapped things just enough for Dataflow to execute a DoFn without much context. The Java SDK harness has the same need, and relies on DoFnInfo. Effectively, DoFnInfo is the UDF that the Java SDK harness understands.

This also helps to break the dependency between the Java SDK harness and the Dataflow runner codebase, by just moving it to be an allowed dependency.

This will require a new worker image.

[kennknowles]

R: @tgroh

[kennknowles]

Run Dataflow ValidatesRunner