UDF lineage?

To be investigated.

> a few points to note from our experiences at Kensu Inc.
>
> you might want consider a few interesting special cases when part of lineage maybe need to be provided semi-manually, e.g.:
> - semi-manual lineage for UDFs, UDF can be matched by `ScalaUDF.function.getClass.getName`:
> - extra UDF inputs that are local files (e.g. H2O predict via spark pipelines)
> - optional annotations for lineage inside UDF if needed, e.g. by default lineage assumes that all input fields of UDF are connected to the output of UDF, but this might be manually clarified
> - making easy to plug-in extra semi-manual/programmable lineage to connect with the external world the parts of plan that may be unresolved by default implementation, e.g. H2O contains `H2OFrameRelation extends BaseRelation with TableScan` which accesses remote H2oFrame not seen by spark directly
> - same above points applies to RDDs
>
> also making easier to customize stuff if needed: avoid private/final methods would be great.
>
> finally, probably some special care needed for struct fields support.
>

_Originally posted by @vidma in https://github.com/AbsaOSS/spline/issues/114#issuecomment-705439880_