Provide a list of untyped fields in Dataflows

[slittle4782]

When building a dataflow it is not uncommon to have fields which Fabric can't immediately detemine a type (e.g. Text, Integer, etc).

Untyped fields prevent the datalfow from publishing.

The error messaging around this really is sub-par.

It would be helpful to identify these untyped fields easily in the UI.

 - e.g. somehow highlight or alter the color of these columns in the UI so that they can be addressed.

 - and/or provide a UI control to identify a list of these fields from any/all tables and allow the user to define the type.