The FunctionArgumentAttr was removed in order to better conform to the
builtin FunctionOpInterface. The FunctionOpInterface exposes the
argument and result types as array attributes of mlir::Type, and this
was difficult when each argument was wrapped in a FunctionArgumentAttr.
Debug names of the function types arguments from the model is currently
lost in the conversion to MLIR, but when the conversion for functions
themselves is implemented, the names can be added to the function
operations as argument attributes.
Alessandro Di Federico